I have seen people struggling on getting the Tablet/Pen or the Pen Displays to work, and they complicated their lives by installing everything related to tablets/wacom/xinput and so … resulting in conflicting settings/services/drivers.
Now we have a wiki page to deal with them, and hopefully will get updated and have more solutions for different issues.
One thing to know for those that have tablets that are compatible with the “kcm-wacomtablet” configuration GUI in KDE Plasma, now that package is in the community repos, so is not necessary to compile it from AUR. I made different tests, in the past few weeks since was introduced to Manjaro repos, to see if is working flawless, and it seems the struggle has ended. There are still a few things you can/have to follow from the wiki page mentioned above.