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
You are very naive if you think that a company located un the US can provide an encrypted messaging service that can be used by anyone including terrorists, druglords and US enemies without the government being able to access the messages. Lavabit was a famous case and had to shutdown because its founder rejected to comply with an order from the US government to grant access to information. If you are using centralized communication service located in the US forget about privacy.
”Lavabit is believed to be the first technology firm that has chosen to suspend or shut down its operation rather than comply with an order from the United States government to reveal information or grant access to information.[3] Silent Circle, an encrypted email, mobile video and voice service provider, followed the example of Lavabit by discontinuing its encrypted email services.[25] Citing the impossibility of being able to maintain the confidentiality of its customers’ emails should it be served with government orders, Silent Circle permanently erased the encryption keys that allowed access to emails stored or transmitted by its service.[26]"
“Levison (founder) explained he was under a gag order and that he was legally unable to explain to the public why he ended the service.[21]”