If you’re waiting for Jellyfin to run some kind of relay like Plex, you’ll be waiting a long time. That takes a lot of money to upkeep, and the demand for people who self-host FOSS and then want to depend on an external service is very minimal, certainly not enough to sustain such a service. I’d recommend just spending a weekend afternoon learning how to set up Nginx Proxy Manager and being done with it, the GUI makes it very easy.