Creating a subdomain for reverse proxy without using up license? Possible?

I know, I get it. A license is there for a purpose, and I will always pay for what is valuable and what makes sense, so this isn’t about getting things for free.

Now that that’s clear, here’s something I do, but need to know the best way to do it.

Let’s say on my Unraid server, I decide to install Nextcloud, or Syncthing, or any other Docker container or Virtual Server that has a web management front end.

Typically, I would just point my browser to my unraid server’s IP with the right port and the interface opens up. However, it’s easier to manage nextcloud if I use https://nextcloud.mydomain.com.

I can do this in Virtualmin, but it uses a license, and I’m only using it for a reverse proxy, not a full actual virtual server.

In the past, I would just fire up a whole entire subdomain under my domain in Virtualmin, then modify the *.conf file for apache so it used the correct reverse proxy.

Now, I need to figure out how to add a subdomain to my Ubuntu 20.04 server running Virtualmin and create the ssl certificate, without using up a license so I can simply create the reverse proxy address.

I don’t know if this is against the licensing agreement for Virtualmin, but it seems like it shouldn’t be.

Either way, I don’t know how to fire up a subdomain in apache without using the Virtualmin creation module for virtual servers, which as we all know, uses up a license, which should be reserved for a true fully functional Virtual Server account.

Anyone know how to do this?