Aside from watchOS 3.2 beta 3, tvOS 10.2 beta 3 and iOS 10.3 beta 3 with a new name and shame list for legacy apps, Apple today seeded a third beta of what would become the fourth major update to Sierra since its launch last fall. macOS Sierra 10.12.4 beta 3 (build 16E163f) with Night Shift Mode and other perks is now available to registered developers.
You can deploy the latest beta over the air on your Mac through the Mac App Store's Updates tab. Today's release is only for developers but a version aimed at public beta testers should drop in the next 24 hours.