I remember you were worried about your ISP messing things up for you, hence the VPN. I would recommend creating a “Virtual Machine” that does all of your downloading to whatever hard drive you’re using. That VM can have proton installed. Then, on your regular computer (not within the VM), you can host Jellyfin with no VPN involved, making it accessible at 192.168.0.xx.

I think this hits your goals without needing to expose Jellyfin to the Internet. Plus it has minimal technical complexity. Your downloading traffic will be VPN protected, but Jellyfin will still be accessible to your local network.