dist-upgrade to 22.04 fails

[alex]

dist-upgrade to 22.04 fails with some errors

In main.log we see:
...
2022-08-21 18:33:43,685 DEBUG Comparing 5.4.0-124 with 5.15.0-46
2022-08-21 18:33:43,778 DEBUG Marking 'ubuntu-desktop' for upgrade
2022-08-21 18:33:44,060 WARNING Can't mark 'ubuntu-desktop' for upgrade (E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.)
2022-08-21 18:33:44,060 DEBUG Marking 'ubuntu-gnome-desktop' for upgrade
2022-08-21 18:33:44,341 WARNING Can't mark 'ubuntu-gnome-desktop' for upgrade (E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.)
2022-08-21 18:34:09,234 ERROR Dist-upgrade failed: 'Broken packages after upgrade: ubuntu-desktop, ubuntu-gnome-desktop'
2022-08-21 18:34:09,250 DEBUG abort called

there are no held packages or partial installs afaik.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.38
ProcVersionSignature: Ubuntu 5.4.0-124.140-generic 5.4.195
Uname: Linux 5.4.0-124-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.24
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Sun Aug 21 20:57:03 2022
InstallationDate: Installed on 2016-08-18 (2193 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to focal on 2022-08-21 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2022-08-06T12:08:22.757492

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Nick Rosbrook (enr0n)]

Reviewing the files from your upgrade attempt, you have installed packages from the deadsnakes PPA. Some of the packages installed are newer than those in the official archive, which is keeping some python packages installed which then prevents the upgrade from being calculated. Please try using the ppa-purge tool to remove packages installed from ppa:deadsnakes/ppa. After that you can try upgrading again and if it still fails open a new bug report. Thanks and good luck!