meshtastic very quickly runs into problems with congestion. at around 100 users in a local mesh it becomes super unreliable and in urban areas it is really hard to use. meshcore (a separate network) tries to fix some of that, but is still tied to lora devices and super low bandwidth.

reticulum is not as mature yet, but its protocol is completely transport agnostic, meaning you can mesh almost anything from bluetooth and local wifi to lora, fibreoptic cables, packet radio and telegraph lines. and most importantly: it is a whole new networking stack, not just a single app like meshtastic/meshcore

Yeah, xmpp is a great protocol, but everyone needs to be in the vicinity of the server

I'm also thinking about the possibility of blocking/hijacking the network by the law enforcement forces. If every device is also a node connecting to each other, they can be more hardly taken down I think.

meshtastic

I'm not so familiar with meshtastic, but wouldn't be more helpful to have something that actually runs on people's phones instead of having a separate device? I mean, as you said, everyone has phones, and with something like the Ripple app (or any other panic button app) you could hide the app or clear its data (or you could do it manually). With meshtastic, in the event of a search, I think you would be more suspicious, I think.