Microsoft is making Windows 10 21H1 build 19043.844 a recommended update for all Beta channel users, which means that the update will be served automatically through Windows update.
Today, Microsoft is finally releasing its first preview for its next Windows 10 feature update, which is version 21H1. It will come in the form of an enablement package, just like the previous update.
Yesterday, Microsoft finally announced Windows 10 version 21H1, and as you'd expect, you can start testing it out right now. You just have to enroll in the Beta channel of the Windows Insider Program.