Microsoft today said that it found a bug in the latest cumulative update for Windows 10 version 1903, which prevents people from upgrading to the latest Fast ring build, which is build 18875.
Build 18875 RSS
As promised, Microsoft today merged the Fast and Skip Ahead rings, releasing the first Windows 10 20H1 preview to the regular Fast ring. The new build number is 18875, and not a lot is new.