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.
Simple answer to the question so far as I can see: in order to connect with someone, you have to video conference with them and show them a code. So the anonymity is only as anonymous as the video conference you use to do that. All of the benefits it claims are merely an illusion.