In so far as communicating without going via the internet. This would work by 2 or more people sharing the same wifi network, but they they talked to each other

In so far as communicating without going via the internet. This would work by 2 or more people sharing the same wifi network, but they they talked to each other would be over Reticulum? Can a wifi mesh with no internet connection be made between different routers / access points? Really I am wondering if people cooperating by operating wifi areas t could expand quickly in more populated places. Perhaps the trick would be to run them all the wifi networks fully open? Yeah basically how does one create a city wide mesh with a few hundred people involved?