Use ppa-purge with each ppa installed, to downgrade to genuine version. Then clean the system via 'gtkorphan' & 'bleachbit' (as root, carefully select options) and reboot. Next the upgrade script should be happier.
** 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/1770882 Title: could not upgrade to ubuntu 18.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1770882/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs