Source: Reddit (1)(2) Update: Dark theme for Google App now fully rolling out The rollout for the dark theme for the Google App was rather random at the time of the first report, likely a result of batch-wise testing.
Google app dark theme toggle on Nokia 6.1 Plus running Android 9 Pie While the region of these users is not instantly clear, a few replies suggest that the feature may be rolling out to a batch of select users in the U.S., UK, and Australia.
A couple of Reddit users report that the dark theme for the Google app is now available without an update from the Play Store.
Back in June, Google had also started rolling out a dark theme for the Google app for certain users but at that time, the theme appeared to be partially applied and limited to only a few screens of the Google app – and only to a few users.
But now, the dark theme is finally rolling out to all Google App users.