I discovered the VIRTUAL_HOST_MULTIPORTS scheme, and although the yaml writing might make it hard to use with env files, it might be the best way we could have to finally make nginx-proxy handle non-http routing properly through its variable API.

From the docs, what I understand is that VIRTUAL_HOST_MULTIPORTS accepts the format:

hostname:
  path:
    port: int
    proto: string
    dest: string

and for multiport, we would need :

• hostname to be able to accept a * wildcard in case we would want the port forwarding to apply to any of the hostnames given in VIRTUAL_HOST
• proto to accept a "blank" value, for instance none
• an ssl variable in case we need TLS/SSL (like in the case of DNS over TLS)
• an external port variable, to define which port nginx needs to listen to. I will let you guys decide how to name this one as I am not good at network nomenclature (of course that means this port will have to be exposed on the nginx docker by the user, unless we can do some magic here, but that's outside of the template edition scope)
• I do not know how the location path would work with non-http port forwarding though, so I would be careful about that one too.