Jellyfin has many different clients developed by different people. These clients all have different features. You'd have to be more specific. If you're talking about the web client, I do know there are improvements to the keyboard shortcuts coming in 10.9, but I'm not sure if subtitles are related to any of them.
This is an accessability feature that has been missing since the change to bring hotkeys in line with YouTube.
There's reference to it in the code, but it's not functional without compiling it yourself when I looked into it last year. That was using JMP iirc.
My dad goes on and on about it. Not been the worst thing mind, it's forced him to get used to his hearing aids now that theyre linked to the TV.
Kodi is the workaround were using for him at the moment, which supports it. But it's a pita having to go around and maintain the installation for him, so id love to see it as well.
Setup:
UnRAID docker (i7-4790k, 24gb RAM) hosted backend, primarily WebOS App on LG-CS for front end.
5.1 audio via Yamaha RX-A1080.
