I have a weirdo square monitor from LG (28MQ780 aka “DualUp”) and I found if the aspect ratio of the tablet and the monitor does not match up, you cannot use the entire screen on your tablet. Normally this does not cause problem (16:9 and 16:10 does not differ too much), but on this extreme case (tablet area: 16:10, monitor: 8:9), this severely limits the usability of the tablet in Wayland.
The tablet I use is Wacom CTH-690.
p.s. I have also tried the OpenTabletDriver under Wayland, but it’s virtually useless, as the “artist mode (the only mode that would read the pen pressure)” seems to be just passing through the tablet input from KDE/Wayland.