If you are ok with Jellyfin being public, then I would just put it in front of an nginx proxy. That way, your nginx proxy will handle SSL termination. With SSL, your ISP won't be able to inspect the traffic directly.

If you are running docker, then I'd recommend jwilder/nginx-proxy and its lets encrypt companion jrcs/letsencrypt-nginx-proxy-companion. It makes putting things behind an SSL proxy very easy! This of course assumes you have a public IP address through your ISP and aren't stuck behind CG-NAT!

A second option is to keep it private then use a VPN (this is what I do). Wireguard can be a good option although setting up each device is a bit manual, since you have to generate key pairs for each of them. This also requires you have a public IP through your ISP or have a public box that bridges your public VPN to your home network. That said, it works really well.

Tailscale is a free, but commercial option built on top of wireguard that makes set up a lot easier. If you are stuck behind CG-NAT this is probably your easiest option.