Ubuntu upgrade halted due to unofficial software packages

[Kenneth]

I run KDE neon User Edition 5.19 18.04 and have a few PPA's active (OBS, Chrome, VirtualBox, etc...).

When I try to upgrade to KDE neon 20.04 I am met by the error "Could not calculate the upgrade" ant the text "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 ..."

As far as I know I do not have any Launchpad PPA's, but I might be unaware. And ppa-purge did not tell me anything about what package might be the problem. Neither did the logs in /var/log/dist-upgrade.

I am by far no power user, and this is as long as I can go on my own. I will probably just reinstall from scratch, but since the error message asked me to report it, I did. Hope it might help in any way.

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
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.16
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: KDE
Date: Thu Aug 13 14:25:34 2020
InstallationDate: Installed on 2020-02-23 (171 days ago)
InstallationMedia: neon user "Bionic" - Build amd64 LIVE Binary 20200220-11:32
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-08-13 (0 days ago)
VarLogDistupgradeTermlog: