I made a mount out of 1" square tubing that bolted (w/ large wingnuts) to a base mounted inside the rear wheelwell of my class C. It positioned an inexpensive propane grille about 12" away from the side of the RV. It actually worked well, was easy to install/remove, quite stable, and I used it for a number of years without any heat damage to the RV. But, there were 2 downsides; First, it was a fixed location, so I could never "cook" anywhere else. Second, it was under the awning and under the dinette window, so there was constant smoke issues both inside and outside the RV.
2 years ago, when I purchased a more expensive grille, I decided to forgoe the mount (rather than modify it to fit the new grille). I have a small outdoor folding table that I put the new grill on, and I can now cook wherever is most convenient, be it next to the RV or out by a picnic table, AND I don't smoke out anyone inside the RV or under the awning.
So after using an RV mounted grille for years, I have since moved away from the setup and am glad I did. YMMV.