As mentioned, the Reporting section includes charts and tables with data describing how all the core Office 365 products are used. In addition, many in-depth reports have also been added to the Security & Compliance section, which deliver detailed audits and accountability for organizations with regulatory compliance needs. There are very few products that are not covered, specifically—Bookings, Forms, Planner, StaffHub, Streams, and Sway.
For a more-or-less complete list of all the reports included in Office 365 Admin Center, plus some helpful tips, visit https://support.office.com/en-us/article/activity-reports-in-the-office-365-admin-center-0d6dfb17-8582-4172-a9a9-aed798150263.