So we’re back to step one lol

As an end user that doesn’t seem to help me? How am I to use a plugin?

PeerTube overall lacks decent support for subtitles, which is my answer to all of the questions. Veronica Explains is (so far) the only channel I make an effort to watch on PeerTube because she provides subtitles.

I’d be more than happy with terrible machine-generated subtitles at the bare minimum since they are enabled by default on YouTube when uploading a video. Accessibility is quite important imo