A cell booster and a wifi extender are two different things. They work on different radio frequencies and transmission protocols.
A cell booster for an RV (or car) is an external antenna with an amplifier that rebroadcasts the cellular signal inside the vehicle. If you only need it while parked, you can have a tall antenna that probably does as much to help reception as the amplifier. Weboost makes some excellent ones.
Wifi boosters are also re-broadcast devices, but they pick up the local wifi signal and re-send that. Wifi uses a completely different radio than cellular, though. Boosting the wifi in a campground is often a waste of time, because the problem is lack of internet bandwidth rather than the inability to get the wifi signal.
I used a UAWIFI extender for the past 6 years while I was careening around in my little old Class C motorhome. The UAWIFI works on a USB port. So I would plug it into my laptop, then stick the antenna on my ceiling inside. Many times it brought in a much stronger signal just being stuck on the ceiling inside.
When I needed more help to pull in the signal, I used an "active" USB cord that was 64 feet long. Sounds like a lot, but I could then run the cord out the window and the antenna up to the top of my RV ladder or up a pole leaning against a tree and pull in the signal. I used PVC plastic plumbing to connect together to make a long pole, then often used gear ties to attach it to the back ladder or tree, in this way I had the antenna up high to pick up a signal typically broadcast from a roof somewhere like the office or laundry. The 64 feet was to run the cord neatly around the RV.
In one camp, the Wifi antenna for some strange reason, worked super well stuck on an inside wall near the floor. Maybe their wifi was broadcast from those low pods rather than from an antenna on a roof somewhere. Anyhow, I went from 2 bars to 5 bars (internet connection).
Many RV parks invest in a Wifi system and they keep it forever, until it completely falls apart and then they might upgrade, so I had improvement in every park I used mine in except on the very rare occasions where my RV spot was already picking up 5 bars on their Wifi.
In camps where the Wifi signal was too weak for my spot, this antenna brought it much stronger into my RV time and time again, so I was plenty happy with it. I was often staying in very economical private camps and many state, Federal and county parks which put in a cheap system, that basically requires one to hike to a spot near their office or laundry to use it. My antenna brought it right to my RV.
Recently I settled down for a spell in a small park where I bought a lot, so I now have Wifi direct. I was told by someone else who ordered one a few months ago, that theirs came directly from the UAWIFI site but when they called back with a question, they were told the owner/inventor had passed away. His site now reads "under construction" something the web hosts often put up when the hosting site goes unpaid. I just know that he made a wonderful product that works for me.
Amazon still sells them but only a few left: