upgrade 18.04 to 20.04; 3rd party packages

[Chris Guiver]

Error report uploaded primarily so I can peruse & hopefully learn from it.

My primary box; dual-boot/alternate 18.04 system....
Cause for sure will be 3rd party as reported...
(I have no idea what's on it; haven't used this install since the early cosmic cycle)

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'.

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: 2.20.9-0ubuntu7.24
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: LXDE
Date: Wed Jun 2 09:28:40 2021
EcryptfsInUse: Yes
InstallationDate: Installed on 2018-07-06 (1061 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2021-06-01 (0 days ago)

[Chris Guiver (guiverc)]

I removed telegram, skype, virtualbox, cool-retro-term packages & commented out sources (& apt autoremove);

I didn't expect issues with costales/anoise, and chose to ignore google/chrome or opera/stable

Again tried to release-upgrade; again 3rd party packages error.

I then removed ubuntu-mate-core & ubuntu-mate-desktop, and noted what was removed... added back redshift-gtk & wallpaper packages; apt autoremove

Now the release-upgrade is downloading/installing...

[Launchpad Janitor (janitor)]

[Expired for ubuntu-release-upgrader (Ubuntu) because there has been no activity for 60 days.]