Microsoft 365 compliance center: Endpoint data loss prevention (DLP) for macOS
Currently available in public preview, Endpoint DLP for macOS extends the activity monitoring and protection capabilities of DLP to sensitive items that are on macOS devices. Once the Mac devices are onboarded into device management, the information about what users are doing with sensitive items is made visible in activity explorer and you can enforce protective actions on those items via DLP policies.
More info: https://docs.microsoft.com/en-us/microsoft-365/compliance/endpoint-dlp-getting-started?view=o365-worldwide#macos-onboarding-procedures