No, your options are really just propane. You can use the 1lb cans for a buddy heater or similar, or use the 20lb bbq tanks that fit your RV. Make the 20lb tank happen.
You need batteries for boondocking multiple days and also solar. solar is fine in southern states in the winter depending on your needs. It works for me even in the forest, which of course is leafless in winter.
Two golf cart batteries are a good investment and are more robust than the marine battery.
The lithium batteries are low enough price that if you camp a lot it can be worth the investment assuming you will stay with it 5-10 years.
Again, solar. Do not get the flexible panels, glass only. 200-400 watts is typical, and an MPPT controller that fits the system. Go 24 volt and let the controller change it to 12. By going 24 you use smaller wire from the panels to the inside controller and the controller is always supplied more than 14 volts. This is running two panels in series. Panels are 18 volts, so thats really 36 volts in series, but it is still called 24 volts. dont try to understand this.