@treego is absolutely correct!
This is going on for years now.
The 0.47.2-linux-x64 and the newest of the nwjs-ffmpeg-prebuilt are not working
This is waisting time of thousands of people every time, not to mention the new users of linux and opera, bashing their heads until they get lucky and find this forum thread or give up.
Luckily, we have the great opera community providing solutions, but no thanks to the problem creators/"developers".
It is time for the Opera-Linux devision to step up before users say to them selves enough is enough! This have happened in the past or did you forget?
@alexs 's solution is working for Opera version 79.0.4143.22 on Fedora 34 Workstation -> download libffmpeg.so
Reminder: substitute the existing libffmpeg.so in directory /usr/lib64/opera with the downloaded one and restart the opera browser
P.S. Thank you @alexs !