disable initial configuration tasks and server manager pop up when an admin logs

Launch MMC.exe and select File -> Add/Remove Snap-in, choose Group Policy and local computer and click ok.

Or gpedit.msc

From the Group policy snap-in, navigate to

Computer Configuration -> Administrative Templates -> System -> Server Manager.

There you will find 3 settings for Server Manager, one of it is the auto launch of Server Manager. Enable the setting. The auto launch of ICT is also available here as well.

For further click here