All the activists i know irl use facebook to coordinate sometimes illegal activity
Big tech and governments are monitoring and recording your eating activities. c/Privacy provides tips and tricks to protect your privacy against global surveillance.
For event management, Framasoft created Mobilizon as a free and federated alternative for Facebook events.
From their blog article announcing this development:
For project management, there is System-D.
I think both are directed to activists. They just don’t have the marketing budgets of centralized web giants so their reach is less important.
For messaging, several alternatives exist. https://gofoss.net/intro-speak-freely/
I also think that a lot of activists sadly do not understand privacy issues. They use Facebook as everybody else just because it works and they don’t have to pay money for it. If they don’t understand the issue, they will not search for a better tool.