> What is the use case?

It's primarily just an experimental system. Demonstrating that fixed infrastructure isn't actually necessary to communicate.

Beyond that, it's a mixture of HAM radio for communicating with people outside of your immediate circle, and disaster prep.

The best realistic scenario I can see for using it is after a sever weather event like hurricane, tornado, tsunami, etc. that takes out significant comms equipment. Having an ad-hoc network pop up using battery powered nodes able to setup a secure comms channel to organise aid deliveries would be a powerful tool. But existing infrastructure is resilient enough that it's not actually necessary in modern times.

Beyond that, it's probably more of an IoT type thing. Setup a bunch of nodes across a significant area of land, run machinery, sensors, etc. remotely via a self-healing mesh network.

Some scary applications come to mind.

For instance, sprinkling a bunch of nodes + sensors in hostile territory should allow for gathering intelligence, guiding drones, setting of fuses...