Alrighty, I have a few more leads (because I'm still obsessing over this):
1. I discovered https://beta.meet.jit.si today, and this #Jitsi version has a "Subtitles" button. It only works if the person speaking is using a Chrome-ish browser, but will display on Firefox. That said, it only works for a few mins before failing...
Edit: Turns out I was at the right place at the right time lol, and they have no plans of offering subtitles in the hosted version (https://github.com/jitsi/jitsi-meet/issues/15247)