On fresh installation of Ubuntu 22, using Opera for video playback can be an issue. So even after installing all things that you may think it could help – it does not work. The solution is to install chromium-ffmpeg and copy its libffmpeg.so library into Opera installation folder.

sudo snap install chromium-ffmpeg
cd /snap/chromium-ffmpeg/xx/chromium-ffmpeg-yyyyyy/chromium-ffmpeg
sudo cp libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so

Be aware that snap installation path differs in few places so check your installation. After copying ffmpeg library, just restart Opera and the video, previously not loading in LinkedIn, will work.