Updated Linux Mint to 20 a while ago, and with it RA accordingly. FFmpeg won’t work now probably due to " libavcodec-ffmpeg.so.56: cannot open shared object file: No such file or directory" according to the log. libavcodec installed is 58, so I guess RA is lagging behind?
How did you install RetroArch?
From PPA, on a Lubuntu install I used an AppImage, same result.
Interesting. I’m not surprised about the AppImage, as they’re kinda loosey-goosey on what libs they include in the package, and this sort of thing happens semi-regularly. The PPA, though, is a surprise. I don’t know how/why it would link against a lib that isn’t available in that distro…