do-release-upgrade from jammy to kinetic fails with "An unresolvable problem occurred while calculating the upgrade. "

[Dave Coombs]

Initially installed focal 20.04, and have successfully upgrade a few times (to hirsute, impish, and jammy) but currently trying to update from jammy to kinetic.

Message shown:
  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'.

This suggests removing any PPA, which (I think?) I have done, but the error remains. Any help would be appreciated -- I can attach any config or log files required that would be helpful, if what is automatically attached is insufficient. Thanks!

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: ubuntu-release-upgrader-core 1:22.04.15
ProcVersionSignature: Ubuntu 5.15.0-56.62-generic 5.15.64
Uname: Linux 5.15.0-56-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.3
Architecture: amd64
CasperMD5CheckResult: unknown
CrashDB: ubuntu
CrashReports:
 640:1000:125:23787022:2023-01-04 13:36:27.269139528 -0500:2023-01-04 13:36:28.269139528 -0500:/var/crash/_usr_libexec_evolution-calendar-factory.1000.crash
 640:1000:125:22364460:2023-01-04 14:22:33.902014017 -0500:2023-01-04 14:22:34.902014017 -0500:/var/crash/_usr_bin_gnome-calendar.1000.crash
CurrentDesktop: ubuntu:GNOME
Date: Fri Jan 6 12:37:25 2023
InstallationDate: Installed on 2020-06-10 (939 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to jammy on 2023-01-06 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2021-05-31T09:17:03.332460