Privacy

Signal collects your IP address and the last IP address you sent a message to. They store that info to maintain their services. They also store your phone number, either of which can be tied back to your identity (in the US, don't @ me, friends from across the pond).

The only thing these reveal is that you use Signal, which is currently still legal. Also, even if a judge ordered Signal to collect outgoing messages for your user, the content of your messages would already be encrypted. So unless your use of the service could be construed as illegal (or perhaps who you're talking to), then it's probably still safe to use.

However, all that said, I still agree that SimpleX is a better choice for activism. No phone numbers or other useful identifiers, uses a series of nodes rather than a central server, expiring contact-adding codes, etc... it's simply better, if you need privacy against external threats.

And there's no reason you can't have both on your phone for different kinds of groups!