This is because you installed python3-gi from some PPA and it provides a version greater than the one in 21.04 or has some dependencies in 21.04 that can't be satisfied. Please install python3-gi from the official Ubuntu archive and try the upgrade again.
** Changed in: ubuntu-release-upgrader (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1956869 Title: Cannot update from 20.04 to 21.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1956869/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs