SimpleX Chat: private and secure messenger without any user IDs (not even random)
simplex.chat
SimpleX Chat - a private and encrypted messenger without any user IDs (not even random ones)! Make a private connection via link / QR code to send messages and make calls.

SimpleX Chat is an instant messenger that is decentralized and doesn’t depend on any unique identifiers such as phone numbers or usernames. Users of SimpleX Chat can scan a QR code or click an invite link to participate in group conversations.

-privacyguides.org

It’s clearly proving to be the most innovative technology when it comes to decentralized communication, in my opinion.