Thanks for your report. You have package from non-official repositories installed which are blocking the upgrade.
In particular python3.6: libpython3.6 3.6.3-1+xenial2 LP-PPA-thomas-schiex-blender libpython3.6-minimal 3.6.3-1+xenial2 LP-PPA-thomas-schiex-blender libpython3.6-stdlib 3.6.3-1+xenial2 LP-PPA-thomas-schiex-blender which is not in Xenial. Please uninstall these packages before upgrading again or revert to a version from the official Ubuntu repository. I'm closing this report. Don't hesitate to file any bug you may find. ** Changed in: ubuntu-release-upgrader (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1763747 Title: Cannot upgrade from 16.04.4 to 18.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1763747/+subscriptions -- ubuntu-bugs mailing list firstname.lastname@example.org https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs