Just out of curiosity, since I’ve had a similar problem, can you try to disable KScreen 2 in your Background Services settings near the startup applications/autostart menu, then try to let your monitors go to sleep?
My monitors always wake from sleep repeatedly on their own on both X11 and Wayland, but disabling it fixes it for me (but also resets my monitor settings on every boot/log in). I’m still working on finding a permanent solution for mine, but if this also acts as a workaround for your issue it might help narrow down the cause a bit.