I already see some misleading terminology. I hope the following helps re Dish. I have no experience with DirecTV nor RVs, lots of expereince with Dish.
Dish has three satellites which comprise the Eastern Arc, generally serve the eastern part of the USA. They also have three different satellites that comprise the Western Arc, generally serving the western USA.
They have numerous other satellites that generally carry "specialty" content such as foreign language stations.
A typical complete service has one Satellite Dish that can be pointed to simultaneously receive either all three Eastern or Western Arc satellites.
If the satellite antenna is indeed receiving all three signals, it is receiving all HD and SD programing other than those "specialty" stations.
The Satellite Dish does NOT output a signal that can be viewed on a TV. Rather it sends a combination of the content from all three satellites via coax cable to a Satellite Receiver. That receiver may be connected to one or more TVs by "wire" in some form - Coax or HDMI or other methods.
To watch a specific station, you need to tune the Satellite Receiver to the desired channel. To change the channel to another offering, you need to change the Satellite Receiver channel to the new station.
Local Channels are included on at least one of the three satellites included in each arc. However, the local channels are carried on Spot Beams - by this I mean they are not transmitted to the entire east or the entire west - but rather are focused on a "spot" on the Earth.
Say I live in NYC. The NYC Channels are transmitted such that they can be received in NYC, NJ, CT, etc. However, a person in Miami would not be able to receive them. Additionally, you must have a subscription to view the NYC Channels so a person in NYC that has not subscribed to the locals would also not be able to view them.
Say that New Yawker packs up his RV and heads south to Miami taking his Dish equipment along. When he reached DC he would likely find that he has lost his NYC local channels because he is no longer in the "spot" area. He would not be able to view the DC locals either - he has not subscribed to them so they are not authorized.
When he reaches Miami, he informs Dish that he is temporarily located in Miami and they turn on those stations and turn off the NYC offerings.
Clearly while in Miami, he will not see NYC local sports or Newscasts - but he'll know it is clear and sunny in Miami.
If you try to tell Dish a bogus Zip code, you may find that your actual location is not in the "spot" for the bogus Zip and you thus end up with nothing viewable for locals.
Someone else may be able to help me, but there used to be National Feeds - Network broadcasts from one station in LA, NYC, or Chicago IIRC. While these were not "locals" per se, it did give you access to network programming.
Hope this helps.