OSMAND+ Offline GPS navigation
I've been using OSMAND+ on Android with excellent results the last month. You can enter your RV specs for special routing just like Garmin.
It has been an excellent companion to the Garmin on the dash for additional routing piece of mind.
I still compare routes with Garmin and Sygic but it has been perfect so far.
Not sponsored, just don't see many posts about this product which surprised me after seeing what it can do.