In new versions of Opera, html5 videos does not show, because in Opera has a poor libffmpeg.so file. The solution is to install chromium-codecs-ffmpeg-extra package and use Chromium’s libffmpeg.so
sudo apt install chromium-codecs-ffmpeg-extra
sudo rm /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so && sudo cp /usr/lib/chromium-browser/libffmpeg.so /usr/lib/x86_64-linux-gnu/opera
The next command must be run after every Opera upgrade, because upgrade brings poor libffmpeg.so back.
A script which requires xterm installed.
#! /bin/sh
xterm -e sudo rm /usr/lib/x86_64-linux-gnu/opera/libffmpeg.so && xterm -e sudo ln -s /usr/lib/chromium-browser/libffmpeg.so /usr/lib/x86_64-linux-gnu/opera
