Our local hardware store has propane, but not all the guys are trained well enough to do fixed (ASME) tanks instead of DOT bottles. The owner can, if he is there, and the senior "yard guy". Same at some of the RV parks we have been to, but most can handle a motorhome fixed tank these days (but I watch them like a hawk, cause they are often poorly trained).
If I need propane (not often) and I'm not in a campground that has it, I usually just check my PC or phone for a local propane service place. Actual LP/propane shops have both the capability and the training to do it right, and usually have enough space to bring in a large vehicle (cause they have larger trucks themselves, for LP delivery or service). If I haven't been by the place by car, I call and ask about access with a 40 foot coach.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL