Kmail 5.6.2 flickers on Wayland, e.g. if you press in the menu bar on File or Help and you scroll through the entries in these lists, you can sometimes not even see the entries in the menu list. Interestingly, you can see a flickering of the complete screen (like an overlay) if you have Kmail full screen and you open then afterwards e.g. Konsole in full screen. Sometimes it is enough to just move the mouse into the Konsole window, sometimes you need to open the menu bar ok Konsole and scroll back and forward from Help to Files as well and then Kmail is painting an overlay/flickering. KDE Frameworks 5.38.0 Qt 5.10 beta (compiled against 5.9.1) Plasma 5.11
Same issues on KDE Frameworks 5.39.0
Same issue on KDE Frameworks 5.40 and Plasma 5.11.3.
I confirm. For me, Kmail can even crash the wayland session.
*** This bug has been marked as a duplicate of bug 387313 ***