MacRumors published a story that Apple has released the fourth beta of watchOS 9.1 to registered developers.

Apple Seeds Fourth Beta of watchOS 9.1 to Developers

Apple today seeded the fourth beta of an upcoming watchOS 9.1 update to developers for testing purposes, with the new beta coming one week after Apple released the third watchOS 9.1 beta. To install ‌watchOS 9.1, developers will need to download the configuration profile from the Apple Developer Center. Once installed, ‌watchOS 9.1‌ can be downloaded through the dedicated Apple Watch app on the iPhone by going to General > Software update. To update to new software, an Apple Watch needs to have 50 percent battery life, it must be placed on the charger, and it needs to be in range of the ‌‌iPhone‌‌. 

Apple Seeds Fourth Beta of watchOS 9.1 to Developers