As long as Signal does not cooperate with local officials this would be also okay when not (like telegram) - but they do.
Which means that your activist group can be anonymized with a search warrant against signal.
https://signal.org/bigbrother/santa-clara-county/
Also Signal is again a central service and it is much better to do this error not again und bring up the next big entity that can screw us over.
@m @rysiek True. A question of threat-model to an extend?
Decentralized E2E is probably always better (at least I can't think of why not).
But it doesn't have much exposure. Like Deltachat, Matrix (there might be an encryption or metadata problem with matrix? (Have not read it yet: https://soatok.blog/2024/08/14/security-issues-in-matrixs-olm-library/) and others.