How to properly set up Syncthing GUI with Nginx?

Hi all! Basically the title: I am configuring a NixOS home lab, and I have all the services behind Nginx. The server is also running Headscale, and the connections to the services (except Headscale) are only accepted from the tailnet. This works for other services, but I really have troubles in making the Syncthing GUI work in this way. What I ended up with is this configuration, that works: { services.syncthing = { enable = true; openDefaultPorts = true; # Accept from everyone, ...