When going through the bug reporting process for update-manager-core you should have been asked a question about whether the "the issue you are reporting one you encountered when upgrading Ubuntu from one release to another?". Did you see that question and if so how did you answer?
Additionally, do you have the package ubuntu-release-upgrader-core installed? ** Changed in: update-manager (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/1907078 Title: ubuntu-bug reports installed package is not installed To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/1907078/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs