Windows Server build 19504

Windows Server build 19504 is an unleaked build of Windows Server Manganese. Screenshots of downloads related to this build were shared on Twitter on 26 October 2019.

Difference from Insider Previews
Apparently, this build was available in both the LTSC and Semi-Annual Channel formats as seen in the screenshots. This is a notable difference from released Insider Previews, as they were only available in the Semi-Annual Channel format.