I’ve just tested our latest 22.1.1 ISO of Plasma Edition and it worked as it should. Most likely you may have some installed from the AUR installed, which may need a rebuild due to Qt5 update. You can check via dependency-checker qt5-base or install rebuild-detector to see what is missing on your end.
I just gave that cmd a run on a fresh 22.1.1, which includes this update. I was able to open KCM Style normally. Hence check if you have added some package from the AUR which does your theming and might need a rebuild for qt5 as mentioned earlier @Ben