Most likely a generator will be required for those who will stay off the grid for long periods if planning to camp in warm weather and use A/C all day. I doubt solar power alone will keep up with A/C. And running a big diesel seems to me not all that practical even if for an hour or two at a time to recharge battery bank.
The luxury motorhomes I’ve seen advertised with Volta system sometimes kept the diesel generator as a back-up or alternate power source.
My guess is that the market for these types of DPs are for buyers who mainly stay in campgrounds with shore power, and occasionally want to boondock at night, or run A/C during day while they nap, or to leave pets inside on hot day, etc...
A portable generator should work as long as inverter/charger doesn’t overload it trying to recharge large battery bank too quickly. Fortunately, many chargers can be programmed to limit current.
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