I've been using KDE since before Wayland was a twinkle in RedHat's eye, so trust me when I say that Wayland has always come across as an afterthought from KDE. I'm not saying it was, but given all the issues KDE users have had with Wayland over the years it sure looked that way. If somebody I loved was having trouble with KDE the first thing I'd ask is if they had accidentally switched to Wayland (usually because of an upgrade). The majority of the time they'd check, sigh, and say yes. Switching back their problems would go away.

Reading this thread makes me want to try KDE/Wayland again, so probably on my next install I'll give it another shot. If it's still crap I think it's time to switch off of KDE.