We have a 2009 Phaeton with a Cummings diesel. It has six 6 volt house batteries. The motorhome has a 2000 watt inverter and has a large residential frig. We did a lot of dry camping last winter in ...
To mostly keep the generator off you are looking at 600+ watts of solar.
One of the big benefits to lithium is they will charge at full speed right to full. No long tapering absorption time like your lead-acid. Another benefit of lithium is there is no requirement to get them 100% full. Lead-acid starts to sulfate and lose capacity if you do not get back to tip top 100% fairly often. Lithium might be the last battery you ever buy.