Getting 400 when accessing Home Assistant through a reverse proxy (dockerized nginx)

Hi. You may need to specify a static ip address for nginx in your docker compose file so that it does not change every time you rebuild your containers. This would be an easier solution than guessing which ip it will rebuild. This appears to be the OP’s problem. I had to switch from nginx and certbot to swag to keep homeassistant on network_mode: host.