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
Yes, phone number should be optional for easy contact discovery, not mandatory. As Threema. You have to provide your ID when buying a sim card.
Not only that, but self-hosting should be an option. It isn’t with signal, which is based and hosted in the US, on amazon servers, and subject to national security letters .