And jip, you are right regarding security. I don't use the chrome lib, because I now got used to the fact, that some videos just don't play back in Opera.
And one advantage for me also is, that those autoplay videos on some website don't play anymore in the background, those are sometimes annoying
So I made peace with this function.

Also, when I want to watch a video which opera doesn't want to play, then I switch eiter to Firefox or mpv-player.

this will only work until Opera jumps to a new major version of Chromium

Regarding the above, this is kind of true, the older version of the lib may still work in some cases when you put it in place of Opera's one under ".../opera" folder. However, you should be aware this is not exactly the right way to use it.
When you keep the lib outdated, you can expose your OS to the security holes (not to mention the other bugs in the lib), which may be already fixed in newer versions. In other words, it is worth to keep this lib updated.

@namichel What I found also if you use the method from @l33t4opera, this will only work until Opera jumps to a new major version of Chromium, but seems to work longer then the previous solution

Source here

Nice, it works !

Bellow the bash used,
Lines 2 and 3 have to be changed depending the result of your first line.

$> sudo find / -name "*libffmpeg.so*" 2>/dev/null
/usr/lib/x86_64-linux-gnu/opera/libffmpeg.so
/snap/chromium/1557/usr/lib/chromium-browser/libffmpeg.so
/snap/chromium/1558/usr/lib/chromium-browser/libffmpeg.so

$> sudo mv /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so /tmp/
$> sudo cp /snap/chromium/1557/usr/lib/chromium-browser/libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so

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:
Tada

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

/usr/lib/chromium-browser

to

/usr/lib/x86_64-linux-gnu/opera

to replace it.

In Fedora 32, which I currently use, the path to Opera is:

/usr/lib64/opera

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:

/usr/lib64/chromium-browser

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

Addendum:

Thanks to @leocg who has stated that in another post:

Have also a looks into this here:

Tada

If you are curious why Opera doesn't playback all videos, also the solution there seems to be the same as I mentioned before.

https://fb.watch/4_jPCUzkMM/

On twitter, for ex
https://twitter.com/arielbogle/status/1384376555711844352
https://twitter.com/TheDGstory/status/1382719510290034693
https://twitter.com/WHO/status/1384432299660480512