It seems that there's an issue with playing YouTube videos in full-screen mode. The button is there but the documentation says “may not work on all non-YouTube sites”, which I read as “won't work except on YouTube”.
I'll look into this some more, but for the moment the workaround is to go to YouTube (via the convenient “YouTube” button at the bottom of the video player) and switch the video to full-screen there. This may all be a ploy to get more people to visit YouTube.
· · Posted by Anselm Lingnau · 19 February 2021 19:40