Windows 10 "Lite" versions based on Build 1904x.1387 (specifically 19043.1387 for 21H1 and 19044.1387 for 21H2) are unofficial, debloated operating systems designed to improve performance on low-end hardware. This specific build is derived from the November 2021 KB5007253 update , which addressed several stability and system issues. Microsoft Support Key Fixes in Build 1904x.1387
To harden the system:
The primary focus of this build was resolving an issue where devices using Windows Hello for Business could not access on-premises resources like file shares. Release Channel: It was initially released to the Release Preview Channel windows 10 lite version 21h221h1 build 1904x1387 fixed
You will not find this on Microsoft.com. Instead, it circulates on: Windows 10 "Lite" versions based on Build 1904x