Update from 17.10 to 18.04 fails

[pbhj]

Running the release upgrader from the tray "alert" the upgrade fails saying it can't complete.

"Can't install 'kubuntu-desktop'
It was impossible to install a required package. Please report this bug [...]"

[That text is transcribed as the actual modal is un-copyable text for some bizarre reason. I guess that's a separate bug.]

Launching from command line as `sudo do-release-upgrade -m desktop -f DistUpgradeViewKDE` gives:

~$ sudo do-release-upgrade -m desktop -f DistUpgradeViewKDE
[sudo] password for pandfi:
Checking for a new Ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife

kde
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
authenticate 'bionic.tar.gz' against 'bionic.tar.gz.gpg'
extracting 'bionic.tar.gz'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
exitMainLoop

It proceeds to offer to start the upgrade, I declined.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: ubuntu-release-upgrader-core 1:17.10.11
ProcVersionSignature: Ubuntu 4.13.0-46.51-generic 4.13.16
Uname: Linux 4.13.0-46-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.9
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: KDE
Date: Tue Sep 18 18:50:16 2018
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to artful on 2018-09-18 (0 days ago)
VarLogDistupgradeTermlog:

[Brian Murray (brian-murray)]

Try installing the kubuntu-desktop package and then performing the upgrade.

[Launchpad Janitor (janitor)]

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