In 2018 Microsoft added an implementation of Signal protocol as "Private Conversations". https://support.skype.com/en/faq/FA34824/what-are-skype-priv...

Also, one thing that was pointed out in that article back when it was raised: as the company controls the application you install, and as the application neds to decrypt the data for you, there is nothing stopping it from processing the E2E-encrypted message and requesting the scan for any URL found from a central MS server. The same is true for Signal, Whatsapp and iMessage for that matter (and others).