I will link to this each and every time this comes up:

https://signal.org/bigbrother/eastern-virginia-grand-jury/

Signal turned over everything they had on this user (which was two time stamps: user creation and last access), and fought the gag order to be able to publish the subpoena and the response. Signal would have to be pretty stupid to lie to a federal court.

Think what you want, but Signal doesn’t have any metadata to turn over.

If I worked for the intelligence agencies I would be capturing all the info going in and out of the signal servers at the infrastructure level.

Even if I couldn't break the encryption I'd have timing and connectivity data.

So, if I were a user, I would always operate on the assumption that info would leak.

In this threat model, the only defense you would have would be an overlay network resistant to correlation attacks where all nodes are involved in routing traffic (like I2P), or a mixnet like Katzenpost.

Getting people to use Tor for everything is hard enough, good luck getting people to use stuff even more obscure.

And how often where the silenced by US law and weren't even allowed to mention such a thing? We will never know.