BUT I'm not sure I'm comfortable opening Jellyfin to the internet, even behind nginx, and I don't want to have to spend time setting things up for them or troubleshooting their issues w/ Jellyfin. I put enough labor into this thing already.

This is still where I'm at too. It's a great service, but the fear of messing something up when opening it up to the internet is too worrying. I'm usually pretty good picking up new tech with easier setups, but when there are 4 different networking techniques with their own pros and cons, at that point it's just easier to just run as a local service.