Cannot upgrade Xubuntu+MATE hybrid 22.04 to 24.04

[TragicWarrior]

Description: Ubuntu 22.04.4 LTS
Release: 22.04

Running do-release-upgrade

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

This was likely caused by:
* Unofficial software packages not provided by Ubuntu
Please use the tool 'ppa-purge' from the ppa-purge
package to remove software from a Launchpad PPA and
try the upgrade again.

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.

Restoring original system state

I've tried all of the normal cleaning of source repos and disabling third-party repos. Nothing really helps. It looks like core pieces of Xubuntu are causing the problem from the logs and that shouldn't be the case.

Last few lines of /var/log/dist-upgrade/main.log are as follows:

2024-09-03 08:26:57,494 INFO installing linux metapackage: linux-generic
2024-09-03 08:26:57,494 DEBUG Installing 'linux-generic' (linux metapackage may have been accidentally uninstalled)
2024-09-03 08:26:57,525 DEBUG Marking 'xubuntu-core' for upgrade
2024-09-03 08:26:58,037 WARNING Can't mark 'xubuntu-core' for upgrade (E:Unable to correct problems, you have held broken packages.)
2024-09-03 08:26:58,037 DEBUG Marking 'xubuntu-desktop' for upgrade
2024-09-03 08:26:58,617 WARNING Can't mark 'xubuntu-desktop' for upgrade (E:Unable to correct problems, you have held broken packages.)
2024-09-03 08:26:58,618 DEBUG Marking 'ubuntu-mate-core' for upgrade
2024-09-03 08:26:59,200 WARNING Can't mark 'ubuntu-mate-core' for upgrade (E:Unable to correct problems, you have held broken packages.)
2024-09-03 08:26:59,200 DEBUG Marking 'ubuntu-mate-desktop' for upgrade
2024-09-03 08:26:59,810 WARNING Can't mark 'ubuntu-mate-desktop' for upgrade (E:Unable to correct problems, you have held broken packages.)
2024-09-03 08:27:00,354 ERROR Dist-upgrade failed: 'Broken packages after upgrade: xubuntu-core, xubuntu-desktop'

Running apt-mark showheld reveals no held packages

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: ubuntu-release-upgrader-core 1:22.04.19
ProcVersionSignature: Ubuntu 6.8.0-40.40~22.04.3-generic 6.8.12
Uname: Linux 6.8.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.6
Architecture: amd64
CasperMD5CheckResult: unknown
CrashDB: ubuntu
CurrentDesktop: XFCE
Date: Tue Sep 3 08:29:09 2024
InstallationDate: Installed on 2021-04-13 (1239 days ago)
InstallationMedia: Xubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to jammy on 2024-09-03 (0 days ago)

[Julian Andres Klode (juliank)]

Somehow lightdm-gtk-greeter is marked for uninstall.

  MarkDelete lightdm-gtk-greeter:amd64 < 2.0.8-2ubuntu1 -> 2.0.9-0ubuntu3 @ii umU > FU=1

Is there a conflict between Ubuntu MATE and Xubuntu in how they configure lightdm perhaps?

[TragicWarrior (bryan-christ)]

Ever since running into this issue, do-release-upgrade acts as if there is nothing new available.

Checking for a new Ubuntu release
There is no development version of an LTS available.
To upgrade to the latest non-LTS development release
set Prompt=normal in /etc/update-manager/release-upgrades.

The ability to upgrade from on LTS version to the next is supposed to be a big advantage for Ubuntu. Until now, it's been reliable.