Comment 7 for bug 1899782

I'm pretty sure this is not a duplicate as no one else on the other bug mention the general protection fault you're seeing.

However, I'm also not sure this is a bug, either.

I installed synaptic (why not just use Muon? it's the same thing—an apt frontend—and comes with the install) and ran synaptic-pkexec and had no issues.

If /var/log/installer/casper-md5check.json exists, then you skipped the file check at the beginning of the installation process and that right there may indicate you have a corrupt installation, which could explain this strange behavior.