I am also on a pretty clean KDE neon 6.1.
Did you try to change a global theme that you have to download (so not stock)? I was/am using the the apple sonoma global theme version 1.7.
It is working, but no Plasma Cotrol Hub and background image. When removed and reinstalled no luck. The only extra i am using is xrdp, which has his own problems from the 6.0 version I installed some time ago.
See the error i get in my first post.