https://datatracker.ietf.org/doc/rfc9420/

Google has announced its support for the RFC 9420 specifications of the Internet Engineering Task Force’s (IETF) new Messaging Layer Security (MLS) standard. According to Google, the latest specification allows for interoperability across messaging services (WhatsApp, Messenger, Google Messages, etc.) and operating systems at scale. The company also promises to make its implementation open source, and available to app developers through the Android code base.