It must be more than Window Manager specific, my Debian KDE Plasma also uses KWin as Window Manager (of course, its the default). So maybe specific to 5.24 ?
Apparently, I'm using KDE 5:20.5 (I say apparently because the version reported by synaptic is 5:111 but kwin gets 4:5.20.5-1 ??). Anyway, Debian unstable, right now, does have 5.24, I will see if I can get it going ....
Davo