Jellyfin removed the ability to change ffmpeg location

[tpralle]

10.8.9 removed the functionality of the text box in the Playback settings.

[joshuaboniface]

It did, ironically implemented by yours truly, but you can still use rffmpeg.

The new way is to provide the path to the rffmpeg ffmpeg symlink as the --ffmpeg argument when starting the Jellyfin server. How to do this depends on the platform, but for Debuntu packages it can be done in /etc/default/jellyfin. Once set, restart the server and, with the recent PR jellyfin/jellyfin#11219 it will take precidence; for earlier versions remove it from encoding.xml as well to force that to apply.