> And who knows if it's actually the software they deploy too.

The whole literal point of the protocol is so that you don't have to trust the server, assuming you trust the client and protocol.

That's true for the fundamental part of sending and receiving messages, but at least one ancillary feature (contact discovery) requires trusting the server. They do have a setup with an Intel SGX enclave for remote attestation but I'm not knowledgeable on the limitations of this, although I understand that there are some.

https://signal.org/blog/private-contact-discovery/

Good point, I was just considering the messaging part. It'd be useful to be able to opt out of contact discovery, as I'm not sure you can do this on the current client.