I am very reluctant to use WordPress at all because I’ve heard terrible things from multiple colleagues. It looks like something that’d get problematic at some point.

Absolutely general purpose. In the most simple terms, email, password hash, and a bit of metadata

This is what I had in mind as well; If you had to how would you add a beamer to this that could use your jellyfin/plex server?

Ideally I’d want a pi or mini pc behind the beamer that I can switch on/off remotely so that part is not always on

Okay I never knew that, I would also accept tips for setting up a star trek beamer though xD