I thought it would be great to spread awareness about this issue, hence I'm sharing it with you here.
In X11 there is a nice feature called "Turn off touchpad while mouse is plugged in" - it's a lifesaver when you have a laptop with big touchpad; me and lots of people with this issue accidentally hit it all the time while typing.
However in Wayland this setting is missing. After some digging people found out that this is not an issue with the libinput driver itself (used for touchpads on Wayland), as it is supporting this feature for a while now; rather it's an issue with the settings app itself, simply not implementing this feature while using Wayland.
Hope this will get attention from the community, as the recognition from the dev's side is minimal.
I do not know about any workarounds but you might have more luck searching for one.
As for other issues, someone mentioned in the issue that the "Disable touchpad while typing" is broken on Wayland too; however both of these issues are not present on X11.
Only other issue I'm having is kde daemon crashing while running pacman -Syu inside Konsole (see this link). Other than that, I was with Plasma more than happy and had no other issues.
@JokaJukka@saturnonice
Have you checked if there is a bug report existing?
If not, please create it, so that we have a chance to have it fixed latest with the new #Plasma6 release.