Access the opnsense webui internally through nginx proxy

[baz]

I setup the nginx plugin as a reverse proxy to access a service from my network externally. To do that I had to change the port of the opnsense UI to 4433 instead of 443, which means I have to specify the port to access it now. I would like to simply use an internal subdomain with no ports, like so: https://opnsense.internal.domain.com.

I tried setting this up with nginx. I created an "upstream server" that points to https://opnsense.internal.domain.com:4433, as well as an "HTTP Server" and "Location". However when I access the domain without specifying a port I get an internal server error:



Any idea why that is? Can I use nginx to route locally without exposing to the outside?

I'm not very good with nginx.