I've had some recent trouble using Evolution (Gnome) under KDE/Plasma.
The issue is that Evolution would give me a KDE error when trying to
open its Help docs. I tried reporting this the KDE BZ but was rebuffed,
then took it up on the Evolution BZ. You can see the discussion here:
https://bugzilla.redhat.com/show_bug.cgi?id=2057454
Although the immediate problem is solved by using a gio setting (Gnome
again), Milan Crha, the main Evolution maintainer, has some suggestions
as to why this happened and what can be done about it in general. It
might be worth someone's time to take a look from the KDE side and see
what they think. I have no strong opinions either way, but this may not
be an isolated case.
poc