Solution is to replace file libffmpeg.so in the opera directory with the working one.
New way
- Get ffmpeg
sudo apt install chromium-codecs-ffmpeg-extra
- Replace opera file with our file
sudo ln -sf /usr/lib/chromium-browser/libffmpeg.so  /usr/lib/x86_64-linux-gnu/opera/
- Restart Opera
And every time when Opera will be updated, run
sudo ln -sf /usr/lib/chromium-browser/libffmpeg.so  /usr/lib/x86_64-linux-gnu/opera/
Old way (but stable)
- Download latest release - [version]-linux-x64.zipfile from here (or try another release)
 
- Find opera directory using - which
 -  user@host:~$ which opera
 /usr/bin/opera
 user@host:~$ ls -l /usr/bin/opera 
 lrwxrwxrwx 1 root root 35 дек  9 01:04 /usr/bin/opera -> ../lib/x86_64-linux-gnu/opera/opera
 
- Extract file - libffmpeg.sofrom the archive you downloaded.
 
- Move lib file to the opera directory - sudo cp -f ~/Downloads/libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/opera
 
- Restart Opera