Check out Briar if you need a secure way of communicating, it's fully end to end encrypted and can send messages via bluetooth to allow you to continue communicating with nearby people even when there is no internet, for example, if a cell phone jammer is being used.
opsec/protest PSA; request
I saw a similar thread by @lotsofhellalove telling people not to organise using twitter, someone should let them know of briar's existence as well
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