I've got a second hand organ (trademark "Content", but there are more) at home with two manuals and (almost full) pedal. They're not expensive. There are three and four manual versions too. More than good enough to learn and practice. And no mistake: professional organists use these too, since practicing at a real organ is hard for them, too. Many (smaller) churches use similar organs instead of pipe organs, because of the economics.

> they're just intermediate representations of a full console with multiple manuals, pedalboard, couplers, reverberant room

They're near perfect recordings with all the features, e.g. https://www.sonusparadisi.cz/en/organs/netherlands/rotterdam...

If you want to hear what people play on their home setup: https://www.contrebombarde.com/concerthall/home/front