Apple seeded the fourth developer beta of watchOS 8 on Monday. It was released alongside new dev versions of iOS and iPadOS 15, and macOS Monterey.
watchOS 8 Beta 4 Available For Developers
Those enrolled in the developer program can get the appropriate configuration profile by going to the Apple Developer Center. The latest beta can then be downloaded via the Apple Watch iPhone app at General > Software update.
The first public beta of wathOS 8 was also released recently.