What versions of Windows Server have you used?

In my practice, I have worked with Windows Server versions 2012 R2, 2016, and 2019. On Windows Server 2012 R2, I configured Active Directory and DNS roles, and also automated tasks using PowerShell. I used Windows Server 2016 for deploying Hyper-V and Windows containers. Windows Server 2019 was used for integration with Azure and security enhancement with new features like Windows Defender ATP.