This was a thing: https://piratebox.cc/start : open WiFi network that's not connected to the Internet, but it had a forum software. I even bought a simple router and got it installed, but I sadly never set it up in public. A friend who was involved with a local hangout got interested in the idea of an "Internet" where you had to physically go to the location to access the content, although I don't think he set it up there either.