I think you don't want to do the "extract embedded subtitles" method, it's slow as hell and downloading external subtitles is much faster than the built-in extract, at least for HDR+4K mkv video which is what we end up with the most. Can take up to a minute for a 40 minute episode to extract the subtitles, which means you'll need to pause for a minute before you can watch with subtitles, with a 5950X CPU.
> which means you'll need to pause for a minute before you can watch with subtitles
The entire point is that it will extract the embedded subtitles ahead of time (when the media is added to the library) so Jellyfin doesn’t have to do it when you want to watch it.