can not upgrade to ubuntu 20.04 lts

[Guillaume]

Impossible d'évaluer la mise à niveau

Un problème insoluble est survenu lors du calcul de la mise à niveau.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Thu Aug 13 14:52:10 2020
InstallationDate: Installed on 2020-02-24 (170 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-08-13 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2020-08-13T14:40:42.188602

[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!