For new YouTube videos... I get this message many times:
Your browser does not currently recognize any of the video formats available. Click here to visit our frequently asked questions about HTML5 video.
I have to take the link and replug it into a different browser to see these videos...
This happened on Opera for Linux.... on various ubuntus 18.04 and 20, and in PopOs 18.04 and now... version 20.04 LTS // Opera is up to date: version 68.0.3618.165