@namichel Sadly I have to disappoint you. It's an old problem on Opera for Linux, that it does not play back all videos.
I would advice you to play those videos in another browsers or use the mpv-player which can play back those videos with its links, too.
This topic was discussed already here:
The only solution for this is currently to have Google Chrome installed and replace Operas libffmpeg.so with the one from Chrome...
But you have to do this after every update by Opera.
So according from that linked post copy the libffmpeg.so from
to replace it.
In Fedora 32, which I currently use, the path to Opera is:
in case the mentioned path before should not exist on your system.
Also if you installed the 64-bit version of Chrome then the path would be:
If those paths shouldn't exist too on your system, then try to search for libffmpeg with file searching programs like e.g. catfish.
Sorry that there is no other solution available...
At least from what I know
Thanks to @leocg who has stated that in another post:
Have also a looks into this here:
If you are curious why Opera doesn't playback all videos, also the solution there seems to be the same as I mentioned before.