Upgrade from 18.04 LTS fails

[Kate Buckley]

do-release-upgrade -m desktop fails with the following message:

Could not determine the upgrade

An unresolvable problem occurred while calculating the upgrade.

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'.

main.log shows:

"ERROR Dist-upgrade failed: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'"

sudo apt-mark showhold doesn't show anything held.

I have removed all the 3rd party PPAs and applications, muon and discover say I have no pending updates, and there are no locked packages.

I have some searching around and it looks spookily similar to bug #1875523. Could it be a regression?

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.44
ProcVersionSignature: Ubuntu 4.15.0-143.147-generic 4.15.18
Uname: Linux 4.15.0-143-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.23
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: KDE
Date: Sat May 15 20:22:13 2021
InstallationDate: Installed on 2019-12-21 (511 days ago)
InstallationMedia: Kubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2021-05-15 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2021-05-15T17:34:29.205732

[Brian Murray (brian-murray)]

Thanks for taking the time to report this upgrade failure. There is currently a new version of the release upgrader available in -proposed which may resolve the error you've encountered. Please run the following command to test the new version of the upgrader:

  do-release-upgrade -p

Please lets us know the results in this bug report. Thanks again and good luck!

[Kate Buckley (blackadderkate)]

When I tried it, I got the following error:

authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'
Authentication failed
Authenticating the upgrade failed.
There may be a problem with the network or with the server.

I managed to track down version 20.04.33 of focal.tar.gz on archive.ubuntu.com, downloaded and decompressed it, and ran it, and am pleased to say the upgrade has worked.