They posted this in their feedback portal yesterday:
https://feedbackportal.microsoft.com/feedback/idea/df49aed2-1573-ec11-8943-0022482f9e90.
"As we have shared, we are working on a native Mac client for M1. We understand that our users are eager for a native M1 build, and we are excited to make it a reality in the near future!
We ask that our users please not use unvalidated, unsupported versions. Recently some sites have published articles about a Microsoft Teams Beta release of a Universal Binary application that runs natively on both M1 and Intel based processors. The information in these articles is inaccurate, and they have no backing from Microsoft.
In the articles, there are links to early builds on our CDN that are for internal use only. We can confirm we are working on delivering a Universal Binary offering of Teams, and the CDN link in these articles does contain a downloadable version.
However, we discourage users from trying this version (and any other versions that do not come from official Microsoft distribution channels), as it is still in the early phases of testing, fixing, and validation.
Thank you."