Some MHs tow a cargo trailer done up as a power station like that.
You can have the portable power station in the truck (but not so neat for going sight-seeing in the truck) and just plug the Rv shore power cord into the inverter in the truck.
You will need to "manage" the 120v stuff in the RV so it does not drain the batteries in the truck too much despite the solar helping in daytime.
12v in the RV can be from its own battery as usual or from its converter. In this case there is no "loop" to the batteries the inverter is on. But the converter can be a big draw on the inverter.
Needs some juggling and the Trimetric won't be showing the state of play for the batteries in the truck to help with the juggling act.