Microsoft has released Windows 10 Insider Preview build 20279 for Windows Insiders in the Developer Channel as of December 14, 2020. This build is largely identical to build 20277, which was released on December 10, 2020. Microsoft wants to test upgrade options to other builds. Windows Insiders who upgraded to build 21277 (RS_PRERELEASE) will not be offered this build because they are on a newer build. The announcement was made on the Windows blog, where you can read about fixes and known issues, as well as other details.
see these Neowin and Windowscentral articles on Win10 build 20279: