To resist an organized group, you communicate the problem (in an anarchist society, communicating the problem of a nascent state seems like the easy part), present evidence of the nature and severity of the problem, and ask people and existing organizations to mobilize.
Whether the next step is obstructing the state peacefully or mass production of munitions, would already depend on how bad the state has got.
As a happy user of Signal (no bugs or incidents from my viewpoint), I regardless chime in to say a word for decentralization. :)
Signal is centralized:
There exist protocols like Tox which go a step beyond Signal and offer more freedom -> have multiple clients from diverse makers (some of them unstable), don’t have centralized registration, and don’t rely on servers to distribute messages - only to distribute contact information.
In the grand comparison table of protocols (not clients), Tox is among the few lines that’s all green (Signal has one red square).