Android beta registration is back, O Dev Preview 2 rolling out now

The only supported devices right now are the Nexus 5X, Nexus 6P, Nexus Player, Pixel C, Pixel, and Pixel XL

https://www.google.com/android/beta?u=0

Source: [Update: Factory images and OTA files] Android beta registration is back, O Dev Preview 2 rolling out now