I would argue that setting up nginx or other reverse proxy servers is outside the scope of Jellyfin. That is an infrastructure concern that is usually going to be very unique to your setup.
I, for example, use Traefik as my reverse proxy which requires a different set of configurations to get it working with Jellyfin. I don't expect the Jellyfin team to provide a guide for every reverse proxy. It would be nice, but I can see how this is out of their scope.
[1] https://github.com/jmshrv/finamp [2] https://github.com/jarnedemeulemeester/findroid