The simple way is to plug in the shore power cord to the inverter, while turning off the converter. Fridge set to propane.
If that works out well, then add a sub panel for the items you don't wish to power from the inverter.
Is the RV a 30 amp service?
How many amp-hours of battery bank do you have?
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.