I tested an upgrade from a fresh and stock install of Lubuntu 16.04 to Lubuntu 18.04 today and the upgrade was successfully calcluated (while yours was not). I also tried installed vlc and some gnome packages you had installed and could not recreate the failure.
I suspect your failure had to do with the xorg packages you had installed from the oibaf PPA. PPA packages regularly cause issues when upgrading from one release to another. ** 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/1772246 Title: Lubuntu upgrade to 18.04 fails from 16.04 & 17.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1772246/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs