I had never heard of this before, then last week I watched a video about it and was hooked. Now I'm seeing it everywhere!

Meshtastic and Meshcore are both cool LoRa-based mesh text messaging that operate in an no-license-required band. While this limits your transmit power, it doesn't prohibit encryption - the inverse of most ham radio rules!

Some cities have thriving communities of Meshtastic and/or Meshcore. You can look at maps of coverage to get a very general idea - in my experience, most Meshtastic nodes are NOT listed, while a good number of Meshcore nodes are.

Meshtastic treats the mesh as dynamic - clients are assumed to always be moving, so transmissions flood between different nodes that are in eachother's reach.

Meshcore has a static layer - repeaters that are assumed to be in fixed positions - and a dynamic layer - companions that move. With fixed and hopefully reliable connections between repeaters, routing paths between two users can be 'cached', which avoid the bandwidth overhead of flood routing.

You can get started with a low cost ($30) transceiver board and an SMA antenna ($10) for the ISM band of your region. Stick it in a box an mount it somewhere high up, and see if you can pick up any other nodes!