MartinR

There seem to be some invalid plasmoids? Or an unfinished update? The error messages like "PlasmaCore.IconItem is not a type" look like a Plasma5 version of some plasmoid as that should by now be "Kirigami.Icon" (see https://develop.kde.org/docs/plasma/widget/porting_kf6/ )

I'm not sure which plasmoid is actually giving the error message, so it might be a third-party one, that's to blame?

As most of the underlying work is in QtWayland, I'd say: yes, it's Wayland only (not being the author nor an expert on display technology, so take my words with some caution). The blog post talks about some stuff that is impossible to do in X11 ("impossible" as in "would require massive changes to X11 itself, which no one wants to do").