@nexayq
Solution is simpler than this one.
You already have needed library on your system.

dpkg -S libffmpeg.so

chromium-codecs-ffmpeg-extra: /usr/lib/chromium-browser/libffmpeg.so
opera-stable: /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so

sudo mv /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so.orig

ln -S /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so /usr/lib/chromium-browser/libffmpeg.so