KDE Neon 20.04: "Could not calculate the upgrade"

[Michael Geselbracht]

I used ppa-purge to remove all (two) PPAs and I removed several packages from external sources. None of this helped.

main.log contains an error message "NvidiaDetection returned a error: invalid literal for int() with base 10: 'server'".

ProblemType: Bug
DistroRelease: KDE neon 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38+p18.04+git20200803.1136 [origin: user bionic]
ProcVersionSignature: Ubuntu 5.4.0-42.46~18.04.1-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
CrashDB: ubuntu
Date: Wed Aug 12 21:40:11 2020
InstallationDate: Installed on 2017-02-20 (1269 days ago)
InstallationMedia: neon user "Xenial" - Build amd64 LIVE Binary 20170209-10:37
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-08-12 (0 days ago)
mtime.conffile..etc.update-manager.release-upgrades: 2019-04-20T22:05:42.484682

[LuisC (luiscardozocarreras)]

Same thing here in Ubuntu Gnome 19.10, trying to update to 20.04.

In main.log says:
ERROR NvidiaDetection returned a error: invalid literal for int() with base 10: 'server'

[Launchpad Janitor (janitor)]

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