Hello!
Many thanks for all these information and insight. Indeed I completely agree with what you state.
Meanwhile, I identified the culprit of plasmashell crashing: a system resource plasmoid I use on the Plasma desktop background. If I remove it, no crashes happen anymore. So the safe solution is to report it to its owner/author. Despite this I was unable to crash and end Eddie GUI gracefully, so I might have misidentified this happening. That said I will keep an eye and report again if I find a reproducible way. And I understand this is beyond your control and thank you very much for the feedback.
Kind regards!