You can make RV solar and alternator charging work. It is complex on post-2014 vehicles. This ongoingly updated article explains how.
Our first solar equipped RV was a rare 1974 Westfalia VW Kombi. We added a single 80 watt Solarex solar module (that then cost $650!). It charged a 100 Ah lead acid deep cycle battery. It (plus the alternator) powered two 20 watt halogen lights, and a 40 watt Engel fridge. All proved to be mechanically and electrically reliable – despite being used mostly off-road.