Basically they have imbeded a metal piece behind the fiberglass and foam!
You can use magnets to find the location or a stud finder to detect the metal. Some stud finders are able to find metal as well as wood, others will also find electrical wires as well! Trace it with painters tape to create a facsimile for you to design your bracket mounting strategy.
Find a quick release TV bracket that you like, which is appropriate to the TV size and weight. Be careful not to over torque the screws as if may strip the hole your self-tapping screw makes when you attach the bracket to the trailer.
Remember that part will stay on the outside of your rig, so pay attention to snagging dangers and dust collection, water seeping issues. More holes are more possibilities of de-lamination etc. So when mounting do make sure the screw holes are sealed and note that fixing and removing the TV to it will create some stress therefore making the water seals more important!
Go camping, enjoy nature, dunno how sharing TV programming figures into that scenario unless you are in the stadium parking lot or some such. A friend has a football party rig with TVs mounted outside 65 inch units for fans to watch the game! NFL ticket holder with his signal provider. Have had outside entertainment centers in various rigs and seldom use em as neighbors are close and so prefer to not annoy any one, besides we were out and about to enjoy nature, hiking, beach and such.
We have been to impromptu movie screenings out in the open by hosts who open their camp site to all in the campground. The outdoor theater closes well before the noted quiet hour for the CG! Free popcorn and byob for "soft drinks". They were using a short throw projection system totally awesome. We all pitched in for a Turkey Hill ice-cream run and Pizza too! This CG is one where most of the campers are regulars during certain times of the year.
RUSTIC is good.
Kudos to those who make Local, State & Federal Parks & Campgrounds possible and to those picking up the slack by Providing Private Campgrounds.