There are a few RV automation threads on Facebook.
1) Forget HomeKit. Probably the worst automation system on the market. Lots of other automation systems support your iPhone / iPad that aren't Homekit based.
2) look at Sonoff, Shelley, Qubino. They have Z-Wave 12 volt compatible relays and dimmers / RGB controllers. Inexpensive too.
3) The most important is the automation controller. But I can't talk about that