[Users] Kubuntu upgrade caused disaster!

[Michael Schwendt]

John, if you could query your package manager and show the specific
packages (with full version-release details) of Claws Mail and its plugins
that are installed, that might lead to something.

The two sections in clawsrc you refer to are about the paths/names of
plugins you've loaded in Claws Mail. You could delete those sections
Plugins_GTK2 and Plugins_GTK3 and start from scratch. But the plugin
packages installed by your system must be compatible with Claws Mail,
of course.