Several options are available, including Microsoft 365 Lighthouse and using APIs to integrate with your tools. See Microsoft Defender for Business and Microsoft partner resources.
Defender for Business integrates with Microsoft 365 Lighthouse for multi-tenant support in a single console (https://lighthouse.microsoft.com). See Overview of Microsoft 365 Lighthouse.
You can use the Defender for Endpoint APIs to integrate Defender for Business with your remote monitoring and management (RMM) tools and your professional service automation (PSA) software. See Microsoft Defender for Business and Microsoft partner resources.