Have not done this yet - but been looking at an HDMI IN to coax OUT convertor to plug into one of the inputs of our coach coax distribution panel.
Now we can plug a DVD player or Firestick or Roku or whatever has an HDMI output into the convertor.
This assumes the TV’s all have coaxial inputs and are digital capable. I don’t s works for any older tube type analog TV’s as I’m thinking the convertor output is digital, hitch all aTV’s are today.
The coax doesn’t care what the signal is, and you generally don’t need 4K resolution for your coaches TV’s (if newer flat screens).
Another approach is getting WiFi capable TV’s, a WiFi hotspot (I’m using a NetGear LB-1121), with a good data plan (I’m using TT&T), and a cheap ASUS router (I’m using an NT-300).
Plug the hotspot into the router, setup the router with good security - turn on TV’s and connect to router.
We watch YouTubeTV, Pluto TV, Plex, Netflix, Amazon Prime movies, etc., etc. and don’t have to deal with a parks RV - as long as we have good AT&T cell service.