So that was interesting... an update to the kwallet-pam package in #Bionic caused me to lose my passwords and authentication for my email client, due to loss of wallet.
They're fixing the issue, but in the meanwhile I had to purge evolution, and manually lose some configuration, then install Thunderbird, and then finally reinstall evolution.
Oh and fsck akonadi to get rid of yet more configuration.
#Kubuntu
All good fun (;*