Brett Powell shows how to query the Power BI Activity Log:
The new Power BI Activity Log makes it much easier for Power BI administrators to access audit log data to monitor and analyze activities occurring within the tenant they support. This blog post describes one solution for accessing, processing, and loading Power BI activity log data as part of an automated process to support ongoing Power BI administrative analysis and reporting.
Brett has a very nicely defined solution and lays it out step by step for us.