Ubuntu 20.04

sudo dpkg --add-architecture i386
sudo apt update
sudo apt install \
    g++-10-aarch64-linux-gnu \
    g++-10-arm-linux-gnueabihf \
    g++-10:i386 \
    libatomic1:i386 \
    libc6-dev:i386 \
    libc6:i386 \
    libstdc++6:i386 \
    python3.9

Remove all default GCC pakages (GCC 9).
Make /usr/bin/gcc a symbolic link to /usr/bin/gcc-10.
Python 3.9 is incompatible with many scripts, so use update-alternatives.
