Windows 11 build 21380

Windows 11 build 21380 is an unconfirmed build of Windows 11 which was shown running on an Acer machine during the 2021 Hong Kong Computer and Communications Festival. A number of photographs detailing the watermark,  and various aspects of the user interface were posted on BetaArchive by member DiaoSlime between 21 and 25 August 2021. The watermark includes the same notice that warns users not to take screenshots of the build, as seen in build 21990. It is the earliest known build to contain the new Start menu first seen in the aforementioned build.

The original photographs only show the right taskbar corner, the Start menu, File Explorer interface and the contents of the  dialog, although the original poster stated that the user interface is very close to build 21996 and later.