I don't mean being able to route to a specific port, I mean to actually change the port the ingress listens on.
Is this possible? How? Where is this documented?
From the kubernetes documentation:
An Ingress does not expose arbitrary ports or protocols. Exposing services other than HTTP and HTTPS to the internet typically uses a service of type Service.Type=NodePort or Service.Type=LoadBalancer.
It may be possible to customize a LoadBalancer on a cloud provider like AWS to listen on other ports.