In addition to Windows 10 Insider Preview build 20257 client release, Microsoft has issued a new Windows Server Preview of the same build number.
The released build is the Windows Server Long-Term Servicing Channel (LTSC) Preview that contains both the Desktop Experience and Server Core installation options for Datacenter and Standard editions.
Windows Server Long-Term Servicing Channel Preview is available in ISO format in 18 languages, and in VHDX format in English only.
This new build resolves an issue with server roles, but still comes with a known issue for the shutdown tracker dialog.
Shutdown Event Tracker is displayed every time a user logs on even when the user is a member of the administrators group and the user has closed the tracker window properly.
Auto Logon does not work correctly in some scenarios.
You will find keys and download links in the official announcement.