Why not just run your own WireGuard instance? I have a pivpn vm for it and it works great. You could also just put jellyfin behind a TLS terminating reverse proxy.
Sounds like a pain to get non technical family members to use.
If you're willing to break the non web app you could always put it behind an authenticating proxy (which is what I do for myself outside of VPN, setting up a VPN on a phone is obnoxious and I only look at metadata anyway on my phone)