And then I read about Meshtasic. Interesting, and I took a deeper dive.

What is it, and is it useful for me?

Meshtastic is a enviornment to let you communicate without WiFi or the mobile network. The communication is slow and text based. All you need is a small device operating with low power in the socalled LoRa frequencies (these depend on your country). I recommend a Heltec V3 - easy to install and cheap.

This device has two purposes: In first it's a transmitting station for your cellphone (via bluetooth) and in second a hub in the mesh network, forwarding all recieved messages to every other available mesh device in the LoRa band.

It is useful for hiking trips, where there is no mobile network available or as a tool in a dystropic scenario to communicate when every other possibility fails. Ususally you need to have a minimum devices in your area to use it. Otherwise you have no connection to another device.

I ordered a couple of these small thingis with batteries, printed housings and started playing around. As expected there were no other meshers near me, so it was more or less useless.
BUT there is a function to gateway it to a relay server on the internetz (called GQTT). So one device was dedicated to send out the stuff via Wifi to the GQTT server, and I was immediately connected to hundrets of other mesh devices.

But I went further. I read about the possibility to set up a small BBS - a bulletin board and mail system. I found two systems:
1. the TC2 Mesh BBS https://github.com/TheCommsChannel/TC2-BBS-mesh (python based)
2. the meshBBS https://github.com/martinbogo/meshbbs/tree/main (Rust based)

I installed both on a raspberry pi and found the 2nd somehow nicer. So now I run a meshtastic BBS shouting out via GQTT .....

The MeshBBS has two operating modes:
In the primary (for all viewable) channel it replies to short commans about the weather or a slot machine and
in the direct messages to my little BBS device you can select a username and log in to send messages to the bulletin board.

So if you can reach my little BBS in Mesh somehow ( 2e20 "Sami" ) come over and stress it a bit.