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Linux printer cupsd broke plasma on Kubuntu 19.10 - no start menu

Kubuntu KDE printer settings
I've just had a problem with Kubuntu where the start menu didn't appear. So it was not possible to launch applications, or pretty much do anything. For anyone that has a similar problem this is how I fixed it.

First identify the problem.

To be able to do some diagnosis you need a shell. To launch Konsole press CTRL - Alt - T

Plasma is the name of the KDE desktop environment that Ubuntu uses. The Plasma shell provides the start menu and handles other tasks associated with the desktop. I there tried to start plasma using plasmashell which failed.
There were a lot of messages, but significantly it broke shortly after a reference to cupsd. CUPS (formally known as Common UNIX Printing System) is responsible for handling printing from Linux. So I stopped Cups using
sudo service cupsd stop
then ran
and this time it worked.

I also want to be able to print so I started the printer configuration page, and restarted cups sudo service cupsd start. This broke plasma again, but I now hand the printer configuration page that allowed me to delete the printer drivers. That alone didn't fix it, although I didn't investigate further as at this point I decided to take a forceful approach of reinstalling the entire printer setup. I removed it using
sudo apt remove print-manager
then reinstalled using
sudo apt install print-manager

I re-added my printer through the printer configuration menu, rebooted and it's now fixed. It turns out this a problem that other have had before, so I thought I'd put it here in case someone else has the same problem. The next version of Kubuntu will be version 20.04 which is due later this month, so it would be interesting to know if they have added a fix so that plasmashell doesn't crash even if there is a problem with the printers.