"Use Signal, Use Tor" were slogans for a while, and while that slogan's use dropped off, Signal is still the go-to messenger for radicals. However, it's not a silver bullet. "Signals Fails" discusses how to use it correctly and common mistakes.
https://www.sproutdistro.com/catalog/zines/security/signal-fails/
A lot of the protest camps that have sprouted have been remarkably autonomous, but the spectre of party based organizing or protest leaders can come in and stomp all over these movements in the name of building a bigger coalition. Affinity Fraud discusses (among other things) that the illusion of a unified left is a genuine security threat to radical movements.
https://opsec.riotmedicine.net/downloads/