What does Jellyfin have to do with that? If you implement acess control in the reverse proxy, requests from non-whitelisted IPs are just not forwarded to Jellyfin.

I have mine behind a revwrse proxy (Nginx Proxy Manager), and use a whitelist to allow specific IPs or IP ranges access so my family can use it.

I use Nginx Proxy Manager and whitelist my remote users. They all have static IPs though, so its a workable solution for me.

Before I used a whitelist I would go through the access logs, and could never find any attempts to exploit the endpoints - only some random bots trying to find some admin page assuming it was another service. Not saying you shouldn’t take it seriously, but you are likely not subject to these attacks the moment you expose it.

That said, there is a discussion about these endpoints on their repo. At some point they will be fixed (my impression is that they are hampered by legacy Emby code). When they do, you could do this more securely.