==== Disclaimer: This is 5 minute quick solition. You may consider using for eg. FFMPEG for Docker instead.
docker build -t unclev/ffmpeg3 .or with custom user:group IDs (1001:1001 for eg.)
docker build --build-arg PUID=1001 --build-arg PGID=1001 -t unclev/ffmpeg3 .ffmpeg within the container is run in the name of a producer user with uid:gid as specified with the build args (1000:1000) by default.
alias ffmpeg3='docker run --rm -v "$(pwd):/home/producer" unclev/ffmpeg3 ffmpeg'