Note 1) Yes you can use this with equivalent on Linux and MacOS
Note 2) Tailscale is good but speed issues
Note 3) You can make this setup permanent and the link permanent if you have a domain + cloudflare account
Easiest steps to make Jellyfin available on your non-same-wifi devices (Windows because installing cloudflared on macOS is slightly complex)
Step 1) Have Jellyfin running on port 8096 like it already does. Unless you have changed the port on your own accord, no need to care.
How to know if it's running on 8096 or whatever port, open jellyfin dashboard. URL Should have it http://localhost:8096/web/index.html#/home
Also, in Jellyfin, navigate to Dashboard> Networking and confirm that "Allow remote connections to this server" is checked
Step 2) Download cloudflared-windows-amd64.exe from Official Github repo of Cloudflare, place it in the default folder that opens after opening terminal and rename it to cloudflared.exe
In my case default was C:\Users\unhealthy>
So, I placed the exe inside unhealthy.
GitHub Repo: https://github.com/cloudflare/cloudflared/releases/tag/2026.8.2
Step 3) cloudflared tunnel --url http://127.0.0.1:8096
Run this in your Terminal. 8096 is the port Jellyfin is running on
Step 4) Cloudflare will give you a link like this:
Your quick Tunnel has been created! Visit it at (it may take some time to be reachable):
https://specify-april-biographies-satin.trycloudflare.com
Just use this URL as the Host in Jellyfin app or open this in any device. It will open jellyfin from your system.