The Opera deb package for Ubuntu has a nasty bug that breaks native support for H.246 videos. It is connected to the fact, that Opera uses chromium’s libffmpeg.so, but the version are not in sync. There have been debates about fixing the issue at Opera forums, but no official patch resulted thereof.
However, a patch exists and – to cut long story short – a hero named Zsolt Csáky decided to simplify it for himself and for the rest of the world, and created a shell script, that does the job in one simple command. He uploaded the script to a public repository on Gitlab and saved the rest of us from messing around and copping codecs.
The project is named OperaFFier and I thank Zsolt on behalf of the rest of us.