https://theintercept.com/2024/03/04/signal-app-username-phone-number-privacy/
New Signal Usernames Help Stymie Subpoenas, Data Priavacy
Mar 6, 2024 - Ephemeral usernames instead of phone numbers safeguard privacy — and makes the Signal messenger app even harder to subpoena.
newsignalusernameshelpstymie