Update to 22.04 failed due to ¿'unavailable sources'?

[Jackalux]

I was updating from 20.04 to 22.04 and don't recall the error message exactly; I allowed it to log the issue which then asked for info from me here after dialogue boxes are gone.

I have no further info but debug info will apparently be appended.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.41
ProcVersionSignature: Ubuntu 5.4.0-156.173-generic 5.4.241
Uname: Linux 5.4.0-156-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.11-0ubuntu27.27
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
Date: Sat Aug 26 19:18:49 2023
InstallationDate: Installed on 2020-04-28 (1215 days ago)
InstallationMedia: Xubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to focal on 2023-08-26 (0 days ago)
VarLogDistupgradeAptlog:
 Log time: 2023-08-26 19:16:51.398010
 Log time: 2023-08-26 19:17:16.627122
 Log time: 2023-08-26 19:18:30.308332
 Log time: 2023-08-26 19:18:54.406264
VarLogDistupgradeTermlog:

[Jackalux (heartwoodjack)]

 I repeated the process; here are the messages:

Third party sources disabled

Some third party entries in your sources.list were disabled. You can re-enable them after the upgrade with the 'software-properties' tool or your package manager.

'Setting New Software Channels' failed before but now it seems to be working. I'll post this and come back to it