@pinportal Thanks!, I should try it. The older 2018 post below, from burnout426, is very similar and it also works on Mint 20, and I haven't noticed any side effects so far:
**burnout426 Jul 5, 2018, 5:35 PM
@drpostman A little bit better directions.
Start Opera, goto, https://github.com/iteufel/nwjs-ffmpeg-prebuilt/releases/ and download the 0.31.4-linux-x64.zip file. In Opera's download dialog, click the folder icon to show the file in the file manager. Right-click it and choose "Extract here". This will give you libffmpeg.so.
Right-click in a blank spot in the file manager and choose "open as root" and type in your password. Then, right-click on libffmpeg.so and choose cut.
Then, in the file manager, browser to "/usr/lib/x86_64-linux-gnu/opera/". Right-click in a blank spot and choose to create a new folder named lib_extra. Once the folder is created, go into it, right-click on a blank spot and choose paste. You should then see libffmpeg.so there. Then, restart Opera and goto https://youtube.com/html5 to see if h.264 support is enabled for example. Then, test out some videos. On youtube, you can right-click on a video and choose "stats for nerds" to see if it's using vp9 or h.264. Or, you can try these h.264 videos to make sure they work.
You can then close the file manager.
(Tested on Linux Mint 19 Cinnamon x64)**