Kwin 5.16 might technically support EGLStreams, but I have an Nvidia card and tried it out - after setting env variable to even make it try to work, Plasma crashed during startup, kicking me back to login. I tried again, and it managed to start up, but then plasma-shell crashed when I tried to search something. Performance varied dramatically, the mouse cursor switched from 60fps to 1fps randomly.

Kwin EGLStreams is not ready.