For those who are running into the same problem, I found a solution for the arm toolchain 12.2. It might also work for the previous version of the toolchain, I haven't checked. 12.2 brings c++ 20 support.

I containerized this as follows

# install dependencies for python3.8
RUN apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev wget -y

# install arm toolchain
RUN ARM_TOOLCHAIN_VERSION=12.2.Rel1
RUN curl -Lo gcc-arm-none-eabi.tar.xz "https://developer.arm.com/-/media/Files/downloads/gnu/12.2.Rel1/binrel/arm-gnu-toolchain-12.2.Rel1-x86_64-arm-none-eabi.tar.xz"
RUN mkdir -p /opt/gcc-arm-none-eabi
RUN tar xf gcc-arm-none-eabi.tar.xz --strip-components=1 -C /opt/gcc-arm-none-eabi
ENV PATH="/opt/gcc-arm-none-eabi/bin:${PATH}"

# test arm-none-gcc
RUN arm-none-eabi-gcc --version

# install python3.8
RUN wget https://www.python.org/ftp/python/3.8.12/Python-3.8.12.tgz
RUN tar -xf Python-3.8.12.tgz
WORKDIR /Python-3.8.12
RUN ./configure --enable-optimizations
RUN make -j 4
RUN make altinstall

#attempt to fix libncursesw.so.5
RUN apt install libncurses5 -y
RUN apt install libncursesw5 -y

# test arm-none-gdb
RUN arm-none-eabi-gdb --version

So it basically :

• installs a bunch of dependencies,
• downloads arm toolchain 12.2
• compiles python3.8 from sources and installs python3.8 next to any existing python version.
• tests if it can execute arm-none-eabi-gdb

If you want to execute this on your host OS, remove the docker RUN commands and add some sudo's here and there :).

If it's of any help, my full docker file (which installs a bunch more, like jlink support to be able to compile/run/debug from vscode when attached to this docker container)

FROM ubuntu

ENV UDEV=on

RUN apt-get update -y
RUN apt-get upgrade -y

# Install dependencies for JLink
RUN apt install libxcb-render-util0-dev -y
RUN apt install libxrender1 libxcb-shape0 libxcb-randr0 libxcb-xfixes0 libxcb-sync1 libxcb-shm0 libxcb-icccm4 libxcb-keysyms1 libxcb-image0 libxkbcommon0 libxkbcommon-x11-0 libfontconfig1 libfreetype6 libxext6 libx11-xcb1 libsm6 libice6 libglib2.0-0 -y

# Install dependencies for JLinkServer
RUN apt install libxcursor-dev libxfixes3 libxrandr2 -y

# install jlink
RUN mkdir -p /home/Downloads
COPY JLink_Linux_V786b_x86_64.deb /home/Downloads/JLink_Linux_V786b_x86_64.deb
RUN dpkg --unpack /home/Downloads/JLink_Linux_V786b_x86_64.deb
RUN rm /var/lib/dpkg/info/jlink.postinst -f
RUN dpkg --configure jlink
RUN apt install -yf 

# Install curl
RUN apt install curl bzip2 -y


# install dependencies for arm-none-eabi-gdb
#RUN apt install libncurses5 -y

# install dependencies for python3.8
RUN apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev wget -y

# install arm toolchain
RUN ARM_TOOLCHAIN_VERSION=12.2.Rel1
RUN curl -Lo gcc-arm-none-eabi.tar.xz "https://developer.arm.com/-/media/Files/downloads/gnu/12.2.Rel1/binrel/arm-gnu-toolchain-12.2.Rel1-x86_64-arm-none-eabi.tar.xz"
RUN mkdir -p /opt/gcc-arm-none-eabi
RUN tar xf gcc-arm-none-eabi.tar.xz --strip-components=1 -C /opt/gcc-arm-none-eabi
ENV PATH="/opt/gcc-arm-none-eabi/bin:${PATH}"

# test arm-none-gcc
RUN arm-none-eabi-gcc --version

# install cmake
RUN apt install cmake -y
RUN apt install udev -y
RUN /lib/systemd/systemd-udevd --daemon

# install git
RUN apt install git -y

# install ninja
RUN apt install ninja-build python3 pip -y
RUN pip install meson

# install python3.8
RUN wget https://www.python.org/ftp/python/3.8.12/Python-3.8.12.tgz
RUN tar -xf Python-3.8.12.tgz
WORKDIR /Python-3.8.12
RUN ./configure --enable-optimizations
RUN make -j 4
RUN make altinstall

#attempt to fix libncursesw.so.5
RUN apt install libncurses5 -y
RUN apt install libncursesw5 -y


# test arm-none-gdb
RUN arm-none-eabi-gdb --version

ARG USER_ID
ARG GROUP_ID

RUN addgroup --gid $GROUP_ID user && adduser --disabled-password --gecos '' --uid $USER_ID --gid $GROUP_ID user
USER user

WORKDIR /home/dev/

CMD bash