[Mashiro]

You can't install multiple control panels within one server without isolating both control panels and everything they run. Attempting so will in almost every way break either one or both control panels and other packages because of conflicts, wrong configurations, mismatching software and other reasons.

So your provider wasn't wrong about Docker. It allows to isolate applications on a server and therefore you can host multiple different instances of control panels, software and so on. Maybe Portainer can help to use Docker easier? Of course you still need to learn how to operate Docker. If mastered it is a awesome product and makes life so much easier thanks to automation.

Or you get a second server. It's a bad idea to run web and gaming servers on a single and the same machine.