Glad to hear you are up and running with HG using the latest Raspbian OS, Raspbian Buster. This is important as the previous Raspbian OS version, Raspbian Stretch will be heading to end of life support so updates available for it will be restricted to security updates for a limited amount of time. You can sit back for at least another three years without worrying about what Raspbian OS version you have.
What you now have is a HG installation unique to you. The problem with using another persons downloaded image is, that persons image could have corrupted configuration files unknown to them. You then inherit those corrupted files and problems that arise with your installation as a result are very difficult to resolve.
Other than your sources list for Mono which i resolved, you saw how quickly the copy/paste method performed. You used exactly the instructions I outlined above. I think it's best that any user who is serious about exploiting HG fully should use this method. The main thing is that it works.
I hope that your new installation now resolves your Ghost RF commands issue. Maybe you could report back later and let us know if it does.
For any other HG users, you should give the above a try. If nothing else it will give you a basic primer in Raspbian and the Raspberry Pi which I imagine @edjal will clearly agree with.