Here's our solution. We considered mounting to the trailer but ruled that idea out years ago. Why? Because the sun causes so much glare you can't see the screen. By leaving it completely portable, you can always get it relocated in a position without the glare.
This one has a flat mount (not an arm) so it can just be lifted off the bracket in the camper and brought outside. Lightweight television, easy to move around. And because it's the same one from our bedroom area, it takes no extra space.
I'll never mount one on the outside.