In this post I talk abut a carillonist who has his own portable one. With vids even:
So that’s one way. Just practice in your garage like all the other teenage grunge band wannabes. 
As to church organs I’ll suggest that although each instrument is unique, they’re only unique-ish. The ideas are consistent. A common electronic organ for home use has 2 keyboards. Each of which can be set by various switches to make different types of sounds. And which switches are generally set once before beginning the piece and leaving them that way. Sometimes a quick change is made along the way, but not often.
A church organ with 4 or 5 keyboards is just more preset sound sets to work with. It’s still only played 2 keyboards at a time, jumping from one to the other now and again over teh course of some, not all pieces.
The foot pedals are simply another set of keys delivering yet another sound. And of course have their own set of knobs and switches to set up.
So overall I’d separate “configuring” the instrument from “playing” the instrument. A lot of what’s hard about playing music is the real-time nature of it. The keyboards themselves are the same, or very nearly so on every keyboard instrument. The configuration process differs largely, but that doesn’t have to be done in real time.
Bottom line:
Kinda like driving a rental car, the specifics of starting the engine, adjusting the seats & mirrors, and setting the HVAC & audio is unique, but once you’re actually in motion, they all drive about the same for the things that matter moment to moment.