The mirror of the Ubuntu archive you use is not an official one and subsequently the release upgrader disabled it.
2020-05-29 19:52:04,649 DEBUG entry '# deb http://mirror.onet.pl/pub/mirrors/ubuntu/ focal main universe restricted multiverse # disabled on upgrade to focal' was disabled (unknown mirror) Please switch to an official mirror of the Ubuntu archive and try the upgrade again. ** Changed in: ubuntu-release-upgrader (Ubuntu) Status: Confirmed => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1881337 Title: 'ubuntu-minimal' could not be located. LTS 18.04 to 20.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1881337/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
