https://wccftech.com/windows-10-update-kb5003698-build-18363-1645-preview-is-out/

Windows 11 may be the most in-vogue topic right now, but Microsoft is also working on the current Windows 10 versions, trying to fix issues and problems. The Windows maker has today released the "C" release Windows 10 update, which is tagged "preview" and isn't a mandatory update.

Today's June 2021 C release preview update is available for Windows 10 version 1909 and version 1809. The company added that the "preview update for Windows 10, version 20H2, Windows 10, version 21H1, and Windows 10, version 2004 will be available in the near term."