Plasma 5.19.90 was released yesterday, see:
It will be tested the next 3 weeks in the kde-next repo.
As always, place kde-next above all in your pacman.conf. If you do not know how to edit pacman.conf, then please don't try to attempt testing betas of Plasma, editing the pacman.conf is the easiest part of this kind of testing.
You will have to remove user-kcm, plasma-desktop now contains conflicting files. Rebuild will be done for either plasma-desktop or user-kcm once it is tested that the new users kcm from plasma-desktop is as complete as users-kcm is.