Error during release upgrade 18.04 to 20.04

[tuqueque]

Update could not be calculated

There was an unsolvable problem calculating the update.

If none of this is applicable, then report this error using
the command "ubuntu-bug ubuntu-release-upgrader-core" in a terminal.
If you want to investigate the problem yourself, the logs in
"/ Var / log / dist-upgrade" contains upgrade details; in
in particular, see "main.log" and "apt.log".

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 4.15.0-117.118-generic 4.15.18
Uname: Linux 4.15.0-117-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Wed Sep 16 09:20:42 2020
InstallationDate: Installed on 2018-09-09 (737 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-09-16 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2020-09-16T07:50:57.843271

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you seem to have enabled a PPA that provides Xorg packages. This will prevent the upgrade as that PPA contains package version numbers greater than the release to which you are upgrading. You can revert the PPA by installing the ppa-purge package from the official Ubuntu archive and then running 'sudo ppa-purge ppa:oibaf/graphics-drivers'. After that you can try upgrading again and if it still fails open a new bug report. Thanks and good luck!