do-release-upgrade not work

[Rene Raule]

Es konnte nicht ermittelt werden, welche Systemaktualisierungen
verfügbar sind

Ein unlösbares Problem trat während der Berechnung der
Systemaktualisierung auf.

Die wurde wahrscheinlich verursacht durch:
* Inoffizielle Software-Pakete, die nicht von Ubuntu bereitgestellt
werden
Bitte verwenden Sie das Tool »ppa-purge« aus dem ppa-purge-
Paket, um Software von einem Launchpad PPA zu entfernen und
versuchen Sie die Systemaktualisierung erneut.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.41
ProcVersionSignature: Ubuntu 4.15.0-128.131-generic 4.15.18
Uname: Linux 4.15.0-128-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.21
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Sun Dec 20 20:31:35 2020
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-12-20 (0 days ago)

[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!