Following up on this old thread.
To the best of my knowledge there is still no official Microsoft doc stating that AAD Connect is fully supported on Windows Server 2019. The doc https://docs.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-install-prerequisites (mentioned in a previus post) still only states that "Windows Server Essentials 2019 is supported" and "The server must be using Windows Server standard or better."
Problem is, the version of LocalDB installed with AAD Connect is "Microsoft SQL Server 2012 (SP4-OD) (KB4091266) - 11.0.7469.6 (X64)" -- Which is not supported on Windows Server 2019(?)
The info @ https://docs.microsoft.com/en-us/windows-server/get-started-19/app-compat-19 lists SQL Server 2014 as the oldest version of SQL Server supported for Windows Server 2019.
So, (why) is AAD Connect seemingly supported on WSRV 2019, even though the version of SQL Server installed (LocalDB based on SQL Server 2012 Express) seems not to be?