Nowadays, a majority of apps require you to sign up with your email or even worse your phone number. If you have a phone number attached to your name, meaning you went to a cell service/phone provider, and you gave them your ID, then no matter what app you use, no matter how private it says it is, it is not private. There is NO exception to this. Your identity is instantly tied to that account.
Signal is not private. I recommend Simplex or another peer to peer onion messaging app. They don’t require email or phone number. So as long as you protect your IP you are anonymous
Prove it, give me ssh access to their centralized server so I can verify that they’re running the code they’ve published. Otherwise this is a “just trust me” claim.
There are 10 websites that publicly publish phone number and identity info, right now. Not even a government, but a random stranger can convert your phone number to your real identity.