When you first install Opera on Linux, there are already a few problems with it. We'll be fixing the problems with videos in this post. On some websites like Twitter, videos won't play at all; or like on YouTube, about 25% of videos won't play there. So what is it that we need to fix, it's the "libffmpeg.so" file that comes with Opera, it needs to be replaced with a new file.
Download a new libffmpeg file.
Open terminal and cd to the Downloads folder where it should be or cd to where you downloaded it.
Type in this command:
sudo cp libffmpeg.so /usr/lib/x86_64-linux-gnu/opera/
After replacement, videos in Opera should be working again.