I know you said semi-auto, and I don't know what current production is like. But, for what you want it for, I like SIMPLE and reliable. My 870 Marine Magnum is my choice for that kind of thing. But, I've had it for many years, so I don't know if current stuff is the same.
For RV'ing your way around the country, it's just hard for me to imagine NEEDING a semi-auto. Unless your travel is a cover for your secret identity as the Punisher... Also hard to imagine any LE having any more of a beef with an 870 MM than any other shotgun you might be transporting, even though it is stainless and has synthetic furniture and an extended mag tube.