WearOS got the booster shot it needed from the launch of Samsung’s Galaxy Watch 4.

Google’s smartwatch operating system has struggled for years to gain traction against not only the might of Apple’s WatchOS but also rival platforms from the likes of Huawei, Fitbit, Amazfit, Garmin, and even Samsung.

Samsung was an early supporter of WearOS but eventually gave up on the platform and switched to its own Tizen-based alternative. Earlier this year, a surprise joint...