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?