There is a meshtastic Lemmy community. I think it has limited functionality. Like text only. IIRC it is low frequency, like 900 MHz or something, and is reliable. You have these walkie talkie looking devices, but they don't do voice that I'm aware of. Also, no issues with needing ham license or any of that. I'd be hard pressed to think there was not a community there that didn't have nodes set up. I don't know about security, but it might be under the radar.
There is a meshtastic map, but smaller networks in your community might not register, which is good.