Starting today, all new AWS Directory Service for Microsoft AD (AWS Managed Microsoft AD) directories run on Windows Server 2019. For current customers with existing directories, you can simply update with just a few clicks or programmatically via API. With this feature, you can initiate updates for existing directories when it’s most convenient, avoiding peak business hours, for example. Additionally, starting in March 2023, AWS will begin automatically updating any AWS Managed Microsoft AD directories to Windows Server 2019.
Source:: Amazon AWS