If you are using NGINX Proxy Manager and are trying to proxy a unifi controller the code exists below

location / {
proxy_pass https://127.0.0.1:8443;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forward-For $proxy_add_x_forwarded_for;
proxy_set_header Upgrade $http_upgrade;
proxy_http_version 1.1;
proxy_set_header Connection "upgrade";
}

Where to apply this code?

Go to the advanced tab and post the code above.

Make sure to fill in your IP information.

Originally found on reddit

Running Unifi controller behind a reverse proxy.
byu/Crashyy inselfhosted