Microsoft has made a preview version of the new Teams client available to commercial tenants worldwide. The preview runs only on Windows and isn’t yet available in browser sessions. Some functionality is missing because it’s incomplete but the new client is faster and snappier than the classic Teams client. To use the preview, you’ll need to enable the new client through a Teams update policy.
https://office365itpros.com/2023/03/28/new-teams-client-preview/
