As a leading voice of the German Pirate party and a member of EU parliament, Patrick Breyer (@echo_pbreyer) has actively opposed the proposed legislation throughout its lifetime.
He (and perhaps also his team?) have maintained a comprehensive, fact-checked summary of the proposal's status, with a practical "What can you do" section:
https://www.patrick-breyer.de/en/posts/chat-control/#WhatYouCanDo
@uburprutser@vivaldi.net brought it to my attention that @edri are collecting signatures for a petition against the proposed #ChatControl legislation:
https://crm.edri.org/stop-scanning-me