I found https://en.m.wikipedia.org/wiki/Mesh_networking which has some existing mesh projects mentioned. I know there are many more somewhere.

The wiki page mentions for example http://broadband-hamnet.org : "Broadband-Hamnet™ (formerly called HSMM-Mesh™) is a high speed, self discovering, self configuring, fault tolerant, wireless computer network that can run for days from a fully charged car battery, or indefinitely with the addition of a modest solar array or other supplemental power source. The focus is on emergency communications."

I recall these different mesh groups used to (probably still do) have regular get-togethers where the network traffic capabilities of the various systems were pitted against each other in a competition.