diff --git a/ml/synthesis/Dockerfile b/ml/synthesis/Dockerfile
index f155e712b..63d4881f5 100644
--- a/ml/synthesis/Dockerfile
+++ b/ml/synthesis/Dockerfile
@@ -4,7 +4,7 @@
 # 
 # The following build stages structure is chosen:
 #
-#     ubuntu:20.04 <-- dependencies <-- build <-- ml-script
+#     ubuntu:22.04 <-- dependencies <-- build <-- ml-script
 #                           ^--- development <-- development-gpu
 #
 #     - "build" builds just NITTA itself
@@ -15,10 +15,20 @@
 # NITTA source code is not added to the image during "dependencies" build stage to avoid breaking build cache for "build" stage which depends on it.
 # Create another stage deriving from "dependencies" if practice shows we really need source code in the image instead of a bind mount.
 
-# if you change the ubuntu version, don't forget to update the CUDA repository in development containers below
-FROM ubuntu:20.04 as dependencies
-
-# constructing environment in a layered fashion to utilize docker build cache
+# if you change the Ubuntu version, don't forget to update the CUDA repository in the development-gpu target below
+FROM ubuntu:22.04 as dependencies
+
+# haskell tooling versions here are for ghcup
+# can be: specific like "9.6.2" | "latest" | "recommended"
+# default: recommended
+# GHC 9.6.2 is needed for the recent fourmolu (0.13.1.0)
+ARG GLOBAL_GHC_VER=9.6.2
+ARG STACK_VER=recommended
+# tried to get a fourmolu-0.12.0.0 like in CI, but stackage has no snapshot with such a version at the moment of writing:
+# https://www.stackage.org/package/fourmolu/snapshots
+# this resolver has fourmolu-0.13.1.0
+ARG GLOBAL_STACK_RESOLVER=nightly-2023-08-23
+ARG PYTHON_VER=3.11
 
 # ---- non-root user setup ----
 # Non-root is needed:
@@ -42,14 +52,16 @@ RUN groupadd ${HOST_GID:+--gid $HOST_GID} devuser \
 USER devuser
 RUN echo "cd /app" >> "/home/devuser/.profile"
 USER root
-# sudo is needed only for development images (and is a security risk), 
-# so we'll omit its installation in images for non-interactive containers and install it later in development images
+# since user will run everything as a non-root user, sudo is required.
+# only for development images though, and it's a security risk, so we'll omit its installation in images for 
+# non-interactive containers and install it later in development images.
 
 # -- initializing app dir --
 # it will be application's workdir and repo root
 RUN mkdir /app && chown -R devuser:devuser /app
 WORKDIR /app
 
+
 # ---- install build tools ----
 # noninteractive is needed to avoid interactive prompts during apt-get install from packages like tzdata
 ENV DEBIAN_FRONTEND=noninteractive
@@ -69,20 +81,24 @@ RUN apt-get install -yq software-properties-common \
 
 # -- haskell --
 # GHCup (https://www.haskell.org/ghcup/) is used to install GHC, Stack, etc.
-# easier to control versions, practically required for development images
-RUN apt-get install -yq build-essential curl libffi-dev libffi7 libgmp-dev libgmp10 libncurses-dev libncurses5 libtinfo5
+# easier to control versions, practically required for development images.
+# !!! Currently recommended GHCup version is installed: it's better to have the latest version for development.
+# !!! It may break stuff in the future. Pin the version if that becomes a pain. See lines with get-ghcup + ghcup-stack integration. 
+RUN apt-get install -yq build-essential curl libffi-dev libffi7 libgmp-dev libgmp10 libncurses-dev libncurses5 \
+        libtinfo5 libnuma1
+# libnuma1 was added to fix linker errors (?) while building the image against aarch64
+# the rest is ghcup deps from https://www.haskell.org/ghcup/install/#linux-ubuntu
 USER devuser
 RUN curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | \
     BOOTSTRAP_HASKELL_NONINTERACTIVE=1 \
-    # GHC 9.4.4 is needed for fourmolu-0.10.1.0. can also be: latest | recommended (default)
-    BOOTSTRAP_HASKELL_GHC_VERSION=9.4.4 \
-    BOOTSTRAP_HASKELL_STACK_VERSION=recommended \
+    BOOTSTRAP_HASKELL_GHC_VERSION=${GLOBAL_GHC_VER} \
+    BOOTSTRAP_HASKELL_STACK_VERSION=${STACK_VER} \
     # DO NOT prepend ghcup's binaries dir to PATH in ~/.bashrc
-    # we'll do it later manually in a way that includes non-interactive ssh shells (required for development)
+    # we'll do it later manually in a way that includes non-interactive ssh shells (required for development with vscode)
     # BOOTSTRAP_HASKELL_ADJUST_BASHRC=1 \
     sh
 
-# adding ghcup binaries to PATH
+# adding ghcup binaries to PATH for image building
 ENV PATH="/home/devuser/.ghcup/bin:$PATH"
 
 # setting up ghcup-stack integration via stack hooks, see https://www.haskell.org/ghcup/guide/#stack-integration
@@ -94,24 +110,9 @@ RUN mkdir -p ~/.stack/hooks/ \
     && stack config set system-ghc false --global \
     # do not fallback to stack ghc installation if ghcup is not available
     && stack config set install-ghc false --global \
-    # update resolver in the implicit global stack project (needed for GHC 9.4.4 for fourmolu-0.10.1.0)
-    && stack --resolver nightly-2023-04-09 clean
-
-# setting up PATH in .bashrc to include ghcup binaries (minding non-interactive ssh shells, see inserted comment below)
-# (sed inserts given text before the matched comment (which should be there by default)
-# if we start a line with #, it gets stripped by Dockerfile parser, so putting \n at the beginning of each line to implement comments
-RUN sed -i '/# If not running interactively,/i # ---- custom non-interactive section start ---- \
-\n\
-\n# We do it here BEFORE checking if the shell is interactive because \
-\n# VS Code runs its server in a non-interactive non-login shell created by ssh \
-\n# and those vars are still needed. .bashrc is still executed in this case. \
-\n\
-\n# ghcup-env \
-\n[ -f "/home/devuser/.ghcup/env" ] && source "/home/devuser/.ghcup/env" \
-\n\
-\n# ---- custom non-interactive section end ---- \
-\n\
-' ~/.bashrc
+    # update resolver in the implicit global stack project (needed for the recent fourmolu)
+    # using this instead of "stack config" to **initialize** the global project (it's not created yet)
+    && stack --resolver ${GLOBAL_STACK_RESOLVER} clean
 
 RUN echo "GHCUP: $(ghcup --version)" \
     && echo "STACK: $(stack --version)" \
@@ -127,14 +128,43 @@ RUN curl -sL https://deb.nodesource.com/setup_16.x | bash \
     && npm i -g yarn \
     && yarn --version
 
+USER devuser
+
 # -- ml --
-RUN python3 -V \
-    && apt-get install python3-pip -yq \
-    && python3 -m pip install --upgrade pip \
-    && pip3 -V
+USER root
+# Python build dependencies (pyenv requires them to build Python from source)
+RUN apt-get install -yq build-essential libssl-dev zlib1g-dev libbz2-dev libreadline-dev libsqlite3-dev curl \
+    libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev
+USER devuser
+# - pyenv -
+# add PYENV_GIT_TAG=v2.3.24 before "bash" to pin the version
+# skipping pinning since it's better for development to have the latest version, although it may break stuff
+RUN curl https://pyenv.run | bash
+ENV PYENV_ROOT="/home/devuser/.pyenv"
+ENV PATH="/home/devuser/.pyenv/shims:/home/devuser/.pyenv/bin:$PATH"
+RUN pyenv install ${PYTHON_VER} \
+    && pyenv global ${PYTHON_VER} \
+    && pip install --upgrade pip \
+    && echo "=== === === PYTHON VERSION: " $(python -V) \
+    && echo "=== === === PIP VERSION: " $(pip -V)
+# - poetry -
+# add POETRY_VERSION=1.6.1 before "python3" to pin the version
+RUN curl -sSL https://install.python-poetry.org | python3 -
+# poetry is installed to ~/.local/bin, which is not in PATH by default
+ENV PATH="/home/devuser/.local/bin:$PATH"
+# it's also added to PATH in .bashrc (see above) for VS Code Server's non-login non-interactive shell to see it
+RUN echo "=== === === POETRY VERSION: " $(poetry --version) \
+    # going to use pyenv's "system" python as venv since we're in a container
+    # should have no problems with permissions since pyenv's python is located in devuser's home
+    && poetry config virtualenvs.create false 
 
 
 # ---- get build dependencies ready ----
+USER root
+# preparing stack build for aarch64
+RUN apt-get install -yq clang lldb lld libnuma-dev
+ENV LANG=C.UTF-8
+
 USER devuser
 
 # -- haskell --
@@ -148,22 +178,53 @@ RUN yarn install
 
 # -- ml --
 WORKDIR /app/ml/synthesis
-COPY --chown=devuser:devuser ml/synthesis/requirements.txt ./
-RUN pip3 install --user -r requirements.txt \
-    && pip3 cache purge
-
+COPY --chown=devuser:devuser ml/synthesis/poetry.lock ml/synthesis/pyproject.toml ./
+RUN poetry install --no-root --only main --compile
 
 # ---- finalizing ----
+# set up PATH in .bashrc to include ghcup and pyenv binaries, yarn and poetry global installs, etc. (with non-interactive ssh shells in mind, see inserted comment below)
+# (sed inserts given text before the matched comment (which should be there by default)
+# if we start a line with #, it gets stripped by Dockerfile parser, so putting \n at the beginning of each line to implement comments
+RUN sed -i '/# If not running interactively,/i # ---- custom non-interactive section start ---- \
+\n\
+\n# We do it here BEFORE checking if the shell is interactive because \
+\n# VS Code runs its server in a non-interactive non-login shell created by ssh \
+\n# and those vars are still needed. .bashrc is still executed in this case. \
+\n\
+\n# ghcup-env \
+\n[ -f "/home/devuser/.ghcup/env" ] && source "/home/devuser/.ghcup/env" \
+\n\
+\nexport PYTHONPATH=/app/ml/synthesis/src:\
+\n\
+\n# adding local bin (poetry, first of all) to PATH\
+\nexport PATH="$HOME/.local/bin:$PATH"\
+\n\
+\n# pyenv config: https://github.com/pyenv/pyenv\
+\nexport PYENV_ROOT="$HOME/.pyenv"\
+\ncommand -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"\
+\neval "$(pyenv init -)"\
+\n\
+\n# yarn global installs location\
+\nexport PATH="$(yarn global bin):$PATH"\
+\n\
+\n# ---- custom non-interactive section end ---- \
+\n\
+' ~/.bashrc
+
+# solve buffering issues with python output for development and CI images
+ENV PYTHONUNBUFFERED=1  
+
 WORKDIR /app
 USER devuser
 
+
 # -----------------------------
 
 
 FROM dependencies AS development
-# ---- target for spinning up a container with development envoronment ---
-# Bind mount of repo root to workdir is expected here.
-# Using them to map live source code from the host filesystem straight into the container. 
+# A target to use for spinning up a container with development envoronment (without GPU support for ML).
+# Bind mount of repo root to workdir is expected here! See related README.md for more info and usage examples.
+# Using bind mounts to map live source code from the host filesystem straight into the container. 
 # Container will pick changes made during development without docker image rebuilds. 
 # Existing container data will be obscured (https://docs.docker.com/storage/bind-mounts/#mount-into-a-non-empty-directory-on-the-container), this is fine.
 
@@ -175,34 +236,44 @@ RUN apt-get install -yq sudo \
     && usermod -aG sudo devuser \
     # it will be passwordless
     && echo "devuser ALL=(ALL) NOPASSWD:ALL" | (EDITOR='tee -a' visudo)
+# remove the sudo tutorial on startup
+USER devuser
+RUN touch ~/.sudo_as_admin_successful
+USER root
 
 # unminimizing the system is required to get a decent teminal experience and dev environment
 # installing common handy dev tools here too
 # git is already installed and updated earlier
 RUN yes | unminimize \
-    && apt-get install -yq man-db htop vim
+    && apt-get install -yq man-db htop vim screen
 
 # installing NITTA dev dependencies
-RUN apt-get install -yq iverilog gtkwave libtinfo-dev
-
+RUN apt-get install -yq iverilog gtkwave
 USER devuser
+RUN yarn global add markdownlint-cli2
+
+# pre-building stack test dependencies not to waste developer's time on that later
+RUN stack build --test --only-dependencies
+# install all python dependency groups (including dev ones)
+WORKDIR /app/ml/synthesis
+RUN poetry install --no-root --compile
+
+# cd ~ to use the global stack project with the recent resolver and required (recent) fourmolu version
 WORKDIR /home/devuser
-# this used to fail with linker errors without libtinfo-dev installed while building ghc-lib-parser-9.0.2
-# fourmolu-0.10.1.0 is pinned because of https://github.com/ryukzak/nitta/issues/242
-RUN stack install hlint fourmolu-0.10.1.0
+RUN stack install hlint fourmolu
 WORKDIR /app
 USER root
 
-# installing and configuring ssh server for remote debugging
-RUN apt-get install -yq screen openssh-server
+# installing and configuring ssh server for remote development
+RUN apt-get install -yq openssh-server
 RUN mkdir /var/run/sshd \
-    && sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config
+    && sed -i 's/#PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config
 
 USER devuser
 
-# GPG commit signing can be troublesome in dev containers
-# proposed workaround is a prolonged gpg-agent passphrase timeout and a helper script to enter the passphrase via terminal
-# default is 3 hours = 3600 * 3 = 10800 seconds
+# GPG commit signing can be troublesome in dev containers - IDEs may not support showing passphrase prompts.
+# Proposed workaround is a prolonged gpg-agent passphrase timeout and a helper script to enter the passphrase via 
+# terminal. Default timeout specified here is 3 hours (10800 seconds).
 ARG GPG_PASSPHRASE_CACHE_TTL=10800
 RUN mkdir -p ~/.gnupg \
     && echo "use-agent" >> ~/.gnupg/gpg.conf \
@@ -210,25 +281,19 @@ RUN mkdir -p ~/.gnupg \
     && echo "max-cache-ttl ${GPG_PASSPHRASE_CACHE_TTL}" >> ~/.gnupg/gpg-agent.conf \
     && echo "#!/bin/bash\
 \nexport GPG_TTY=\$(tty)\
-\necho test | gpg --sign > /dev/null" >> ~/passphr.sh \
+\necho anystring | gpg --sign > /dev/null" >> ~/passphr.sh \
     && chmod +x ~/passphr.sh \
     && chmod 600 ~/.gnupg/* \
     && chmod 700 ~/.gnupg
 
 # needed for python code in docker-entrypoint-dev.sh
-RUN pip3 install --user shutup
+RUN pip install --user shutup
 
-# prevent conflicts with previously build artifacts
+# prevent conflicts with previous build artifacts
 RUN stack clean
 
-# adding PYTHONPATH to .bashrc, including non-interactive ssh shells (like one spawned by vscode)
-RUN sed -i '/# ---- custom non-interactive section end ----/i export PYTHONPATH=/app/ml/synthesis/src:$PYTHONPATH\n' ~/.bashrc
+RUN echo "alias pass=~/passphr.sh" >> ~/.bash_aliases
 
-RUN echo "alias python=python3" >> ~/.bash_aliases \
-    && echo "alias pip=pip3" >> ~/.bash_aliases \
-    && echo "alias pass=~/passphr.sh" >> ~/.bash_aliases \
-    && echo "PATH=$PATH:/home/devuser/.local/bin" >> ~/.profile 
-    
 ENTRYPOINT ["ml/synthesis/docker-entrypoint-dev.sh"]
 
 
@@ -236,31 +301,28 @@ ENTRYPOINT ["ml/synthesis/docker-entrypoint-dev.sh"]
 
 
 FROM development as development-gpu
-# ---- includes GPU support (tensorflow-gpu) for development container (possible only on Linux / Windows-WSL2 as of 2023.02)---
+# ---- includes GPU support (tensorflow) for development container (possible only on Linux / Windows-WSL2 as of 2023.02)---
 USER root
 
 
 # ---- check if expected tensorflow version matches requirements.txt ----
 # this should be in sync with version in requirements.txt
-ARG TENSORFLOW_VER=2.12.0
+ARG TENSORFLOW_VER=2.12.*
 # those should be in sync with TENSORFLOW_VER, taken from https://www.tensorflow.org/install/source#gpu
-# cuDNN must be a 8.6 for this tensorflow version, but we also need to specify minor version. you can get it from "Available libcudnn8 versions" output below.
+# cuDNN version must correspond to chosen tensorflow version, but we also need to specify minor version.
+# you can get it from "Available libcudnn8 versions" output below.
 ARG CUDNN_VER=8.6.0.163
 ARG CUDA_VER=11.8
 
-RUN [ $(grep "tensorflow~=$TENSORFLOW_VER" ml/synthesis/requirements.txt | wc -l) = "1" ] || { echo "Tensorflow version mismatch, cannot continue. Tensorflow version was updated in requirements.txt, but not in the Dockerfile. Grab cuDNN and CUDA versions from https://www.tensorflow.org/install/source#gpu and update the Dockerfile near this check."; exit 1; } && \
-    echo "Tensorflow version matches requirements.txt, reinstalling tensorflow $TENSORFLOW_VER with NVIDIA GPU support (cuDNN $CUDNN_VER, CUDA $CUDA_VER)."
+RUN [ $(grep "tensorflow = \"${TENSORFLOW_VER}" ml/synthesis/pyproject.toml | wc -l) = "1" ] || { echo "Tensorflow version mismatch, cannot continue. Tensorflow version was updated in pyproject.toml, but not in the Dockerfile. Grab cuDNN and CUDA versions from https://www.tensorflow.org/install/source#gpu and update the Dockerfile near this check."; exit 1; } && \
+    echo "Tensorflow version matches pyproject.toml installing dependencies for NVIDIA GPU support (cuDNN $CUDNN_VER, CUDA $CUDA_VER)."
 
 
 # ---- installing GPUs-specific dependencies ----
 
-# -- replacing tensorflow with tensorflow-gpu --
-RUN pip3 uninstall -y tensorflow \
-    && pip3 install --user "tensorflow-gpu~=$TENSORFLOW_VER" 
-
 # -- installing CUDA Toolkit required for tensorflow-gpu --
 RUN apt-get install -yq wget \
-    && wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/cuda-keyring_1.0-1_all.deb \
+    && wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2204/x86_64/cuda-keyring_1.0-1_all.deb \
     && dpkg -i cuda-keyring_1.0-1_all.deb \
     && rm cuda-keyring_1.0-1_all.deb \
     && apt-get update -yq
@@ -314,5 +376,4 @@ FROM build AS ml-script
 COPY --chown=devuser:devuser examples examples/
 COPY --chown=devuser:devuser ml ml/
 ENV PYTHONPATH=/app/ml/synthesis/src
-ENV PYTHONUNBUFFERED=1
-ENTRYPOINT ["python3"]
+ENTRYPOINT ["python"]
diff --git a/ml/synthesis/docker-entrypoint-dev.sh b/ml/synthesis/docker-entrypoint-dev.sh
index 7839779dd..0b04517b4 100755
--- a/ml/synthesis/docker-entrypoint-dev.sh
+++ b/ml/synthesis/docker-entrypoint-dev.sh
@@ -10,38 +10,27 @@ if [ ! -f "$ssh_key_location" ]; then
     echo "New key can be found at <repo_root>/$ssh_key_location, it will be automatically authorized in the container on every launch."
 fi
 mkdir -p "$HOME/.ssh"
-cat "$ssh_key_location.pub" >> ~/.ssh/authorized_keys
-
-jupyter_port=${JUPYTER_PORT:-8888} 
-jupyter_token_filepath=ml/synthesis/.dev/jupyter_token
-if [ ! -f "$jupyter_token_filepath" ]; then
-    jupyter_token=$(python3 -c "import secrets; print(secrets.token_hex(24))")
-    echo "$jupyter_token" > "$jupyter_token_filepath"
-else
-    jupyter_token=$(cat "$jupyter_token_filepath")
-fi
+# create authorized_keys if the file doesn't exist
+[ ! -f ~/.ssh/authorized_keys ] && touch ~/.ssh/authorized_keys
+# append the key to authorized_keys if it's not already there
+grep -qxF "$(cat "$ssh_key_location.pub")" ~/.ssh/authorized_keys || cat "$ssh_key_location.pub" >> ~/.ssh/authorized_keys
 
 # make profile settings available in this script
 [ -f ~/.profile ] && . ~/.profile
 
 # start a ssh server as a screen daemon
 screen -dmS sshd sudo -s /usr/sbin/sshd -D
-echo "SSH into this container if needed for remote debugging in IDEs: ssh -i $ssh_key_location -p 2222 -o "UserKnownHostsFile=/dev/null" -o "StrictHostKeyChecking=no" $(whoami)@localhost"
-
-# start a jupyter notebook server as a screen daemon
-screen -dmS jupyter-notebook jupyter notebook --port $jupyter_port --NotebookApp.token="$jupyter_token" --ip 0.0.0.0
-echo "Jupyter Notebook should be available at: http://localhost:$jupyter_port/?token=$jupyter_token"
+echo "SSH into this container for remote development in IDEs: ssh -i $ssh_key_location -p 31032 $(whoami)@localhost"
 
 # print info about GPUs available to Tensorflow
-python3 -c "import shutup, os; shutup.please(); os.environ['TF_CPP_MIN_LOG_LEVEL'] = '3'; import tensorflow as tf; gpu_count = len(tf.config.list_physical_devices('GPU')); print(f'Num of GPUs available to Tensorflow: {gpu_count}')"
+python -c "import shutup, os; shutup.please(); os.environ['TF_CPP_MIN_LOG_LEVEL'] = '3'; import tensorflow as tf; gpu_count = len(tf.config.list_physical_devices('GPU')); print(f'Num of GPUs available to Tensorflow: {gpu_count}')"
 
+# remove defunct screens
 screen -wipe > /dev/null
 
 echo "Available screens (attach with screen -r <name>):"
 screen -ls | sed '1d;$d'
 
-# remove the sudo tutorial on startup
-touch ~/.sudo_as_admin_successful
 
 # fallback to shell for interactivity
 TERM=xterm-256color /bin/bash