One of those BBQs came with my Jayco 19RD TT (metal sided TT) The bracket was already installed on my Jayco TT. We used that way for a year and never had any problems. However, I wouldn't go out and buy one just to mount to the side of any RV. JMHO. The inconvenience is no work area along side of the unit and since I close off some air and smoke my chicken there is too much smoke too close to the RV. That is important for me.
The unit that came with my TT was of such good quality that I kept it and still use it on a table. It has that option. Many of the BBQs I have seen on the market that are portable don't have enough room to BBQ a whole chicken. Being specific, I looked at Webers. Fancy rounded cast 21st century design but not enough room for a whole chicken or much else in them.
Bottom line, I would be looking for a BBQ with lots of interior space, i.e. large square design, and has a thermometer. Home Depot sells the thermometer. Just drill a hole and bolt it in. Take off the regulator and get a long hose that connects to your RV propane tank with the quick disconnect. I have a 23 ft hose.