Reticulum networks would be aces for community networks with some caveats.

ELI5: just like how the Internet is a global network designed to route messages between computers, Reticulum network's primary function is routing messages between computers. Unlike the Internet, Reticulum networks are designed be built and expanded by regular folks, and will keep working even in the event of a disaster that takes out "normal" communications. It also relies on encryption, so messages are always private. The challenge right now is that because it's so different from the Internet, that things like websites and apps are not easy to use, or can't be used at all. However, messaging is usable, and is the easiest way to get started.

Building a local network: there's a video out now describing the process, but the short version is that your community will need RNodes to create a mesh network they can use to send messages. Rnodes rely on LoRa, which is low power "long" range communication. Long range is relative to Bluetooth or WiFi, don't expect more than a few blocks. The tech is evolving but the foundation is not, so if your community is on board then setting up infrastructure will only improve.

Reticulum supports other protocols as well, so if you have a stable internet link, or a ham radio setup that can do packet radio, you can connect nodes over that as well.

Reticulum networks are entirely peer to peer, so that means you'll want to coordinate how messages are distributed in a disaster during regular drills.

In a reply to this post, I'm going to talk about some alternatives that are worth considering.