I've been running plasma 5.10.2 for sometime on a laptop that I
use mainly for
testing and it runs quite well. I have the _copr_mkyral-kf5-unstable.repo and
_copr_mkyral-plasma-unstable.repo installed/enabled from
https://copr.fedorainfracloud.org/coprs/fulltext/?fulltext=mkyral.
You could try enabling those repos and updating to 5.10.2 and see if thing improve.
Thanks for the idea but I get the same issue with your versions! it
just takes more time to logout with Ctrl+Alt+Suppr.
I am hopeless. For now, I use LXDE but it does not work as well as KDE
(before). For example, I have no default pdf viewer installed, no
sound volume icon...
Frédéric