I've had my basic organ lessons on the harmonium, but I'm actually an autodidact when it comes to playing an organ with multiple keyboards and pedal, which I did quite actively from my 20-40th years, and then I changed to a keyboard for accompanying my daughter who played the violin. From my 40-60th I've done nearly nothing regarding playing the organ, but in 2016 I discovered Hauptwerk, so I started first with my old keyboard and got more and more enthusiastic about all the options. So, now I have a nice 3 manual organ with 30-keys pedal.
I improved my 'old' level of skills again ;-)