Initally upgrade stopped for extra PPAs which I removed and tried upgrade again without rebooting. It generated this error as unresolvable error.

[Abhijit Bhattacharyya]

I tried to upgrade from 18.04 to 20.04 which stopped for the first time with advice to remove extra PPAs. I remove from software manager and tried upgrade which generated this error.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.39
Uname: Linux 5.6.4-050604-generic x86_64
NonfreeKernelModules: vtsspp sep5 socperf3 pax
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Wed Sep 30 22:22:17 2020
InstallationDate: Installed on 2019-11-29 (306 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-09-30 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2020-05-26T21:50:04.292544

[Brian Murray (brian-murray)]

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.

[Launchpad Janitor (janitor)]

[Expired for ubuntu-release-upgrader (Ubuntu) because there has been no activity for 60 days.]