if you have an exporter emitting metrics your Prometheus/UCS dashboard database installation should be able to reach it, there is no definitive need to make this available via subdomain.
The article makes use of the Apache Proxy Pass to make the metrics available via LDAP auth on port 443, to enable this Apache has to be configured accordingly with the given file.
The custom target is defined as follows: If your metrics are reachable under
https://A/B/C) the target should look like
You can always look into the defined targets from the Prometheus Web UI too.