Removing from software manager is not the same things as removing the packages from the PPA. You still have packages installed from the oibaf- ubuntu-graphics-drivers-bionic PPA. Those packages are preventing the upgrade from being calculated. You need to reenable the PPAs and then use the tool ppa-purge from the ppa-purge package to remove those PPAs.
** 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/1897943 Title: Initally upgrade stopped for extra PPAs which I removed and tried upgrade again without rebooting. It generated this error as unresolvable error. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1897943/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs