Microsoft has released SimuLand, an open-source lab environment to help test and improve Microsoft 365 Defender, Azure Defender, and Azure Sentinel defenses against real attack scenarios. SimuLab test labs are designed to help security teams understand the underlying behavior and functionality of adversary tradecraft. Microsoft also wants to add automation of attack actions via Azure Functions in the cloud, telemetry export and share, Microsoft Defender evaluation labs integration, as well as infrastructure deployment and maintenance using CI/CD pipelines with Azure DevOps.
Source: https://www.bleepingcomputer.com/news/security/microsoft-releases-simuland-a-test-lab-for-simulated-cyberattacks/