A new report is available in Teams Admin Center for organizations that want to keep track on what version of Teams their users are running, and in specific if they are using Teams Classic or the New Teams app.

  1. In the Teams admin center, go to the Analytics & Reports > Usage Reports page.
  2. From the Usage Reports page, choose the Teams desktop client usage report, choose a date range selection, and select Run report.

Read more: Microsoft Teams new client usage report