Update from 18.04 to 20.04 not possible

[Hanky]

I removed all PPAs with ppa-purge, as well as (hopefully) all packages created by myself.

1) Ubuntu release:
lsb_release -rd
Description: Ubuntu 18.04.5 LTS
Release: 18.04

2)Package version
ubuntu-release-upgrader-core 1:18.04.40

3) Obviously I expected an upgrade to 20.04

4) Instead the upgrade process stopped with an error, telling me that the program was not able to determine which system upgrade was available, and that an unsolvable problem occurred - without further informations what the cause of the problem could be.
It asks me to file this bug report.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.40
ProcVersionSignature: Ubuntu 5.4.0-52.57~18.04.1-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 27 18:59:02 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 2020-10-27 (0 days ago)
VarLogDistupgradeTermlog:

[Brian Murray (brian-murray)]

You still have libsane packages installed from a PPA, those'll need to be removed.

libsane 1.0.31+git20201026-bionic0 0
libsane-common 1.0.31+git20201026-bionic0 0
libsane-dev 1.0.31+git20201026-bionic0 0
libsane-hpaio 3.17.10+repack0-5 1
libsane1 1.0.31+git20201026-bionic0 0

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you seem to have enabled a PPA that provides sane 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:sane-project/sane-git' or 'sudo ppa-purge ppa:sane-project/sane-release' . After that you can try upgrading again and if it still fails open a new bug report. Thanks and good luck!