Nginx Proxy Manager and Fritz Box Port Forwarding

Configuration
5

You haven’t shared how your complete infrastructure looks, but according to this:

you may need to modify your configururation.yaml to enable reverse-proxy support for home assistant.
Mine looks like this:

http:
  use_x_forwarded_for: true
  trusted_proxies:
    - 172.18.0.0/24

(My HA instance is running in a docker container on the host network and the proxy is on a separate docker network, thats why I use this IP range but you should modify it to suit your needs)