One exception:

The Serval mesh project is specifically meant to address the situation of no Internet or cell access. Caveat: it hasn't been updated recently and the Google app store no longer has it. It is still available via F-Droid. It looks like it may be useful if one has a working network that is not connected to the Internet (or has a very poor connection).

https://servalproject.org

https://servalpaul.blogspot.com/2018/11/serval-chat-ios-port-finally-emerges.html

https://f-droid.org/en/packages/org.servalproject/



On Thu, Sep 2, 2021, 11:07 Sean Donelan <sean@donelan.com> wrote:

Another reminder....

Walkie-talkie apps on smartphones, like Zello, still require working
Internet access.  They don't work without cell or wifi service and
internet access.  Zello keeps reminding people, it REQUIRES internet
access; but people don't get it.

https://www.reuters.com/article/factCheckNew/idUSL1N2Q31SN


Only about 5% of households have a NOAA/Weather radio with battery backup
(slightly higher in tornado alley).