I have my JellyFin on a dedicated server outside my home. I use a domain, with and SSH certificate. Before I moved to the domain and the cert I just had an IP:Port setup. At that time JellyFin worked perfectly fine with the windows app, but after moving to the domain and adding an SSH cert, it no longer wants to connect. It works perfectly fine in FIreFox though, so I’m curious if it’s worth trying to figure out why it won’t work in the app, or is using FireFox just as good.
You don’t need to give them access to a internet connection, just the local device. There are many options for this including Netbird, Tailscale, and just plain old wireguard.