Hong Kong protestors using Bridgefy's Bluetooth-based mesh network messaging app
No closed source mesh networking can be secure. However good user experience it has. They are no different than using WhatsApp. Indeed in that respect at least Signal is better.I am not sure why protestors did not adopt the open source serval mesh project apk and ios app. [1]In Hong Kong given the density of building it's bit hard to have a line of sight, so it will still be hard to build a local network. But it's still possible to build a completely  wireless network over the top of the buildings to communicate with each other.This communications can be blocked, but then it will still work if enough people switch on their mobile phone and WiFi router to communicate with each other over peer to peer network which is a combination of wired and wireless. [2] [3] [4] [5] [6][1] http://www.servalproject.org/[2] https://ssbc.github.io/scuttlebutt-protocol-guide/[3] https://dat.foundation/[4] http://subnodes.org/[5] https://hyperboria.net/[6] http://www.servalproject.org/