Now that I have your attention: the binary of KWin/5 just got renamed from “kwin” to “kwin_x11”. For you as a user nothing changes, the startup is adjusted to start kwin_x11 instead of kwin. Nothing else changed. The D-Bus interface is still org.kde.KWin, the config file is still “kwinrc”, etc. etc. Only if you start KWin manually remember to run “kwin_x11 –replace &” instead of “kwin –replace &”.
Say thanks to Hrvoje Senjan for preparing the patches to rename the binary and adjust all the places where the binary name is used.