Comment 3 for bug 1921593

You seem to have installed some packages from the release of Ubuntu to which you are trying to upgrade (Ubuntu 20.04) on your system and that is likely breaking the ability to calculate the upgrade. The problematic packages are likely libpython2-stdlib python-is-python2 python2 and python2-minimal. Please try removing those packages and then upgrading again.

The complete list of strange packages follows:

Installed in the clone-file but not in the system:

borgmatic gcc-10-base libcrypt-dev libcrypt1 libgcc-s1 libpython2-stdlib python-is-python2 python2 python2-minimal python3-pykwalify