Apple’s developer seeds primarily focus on bug fixes and new feature implementation.
Speaking of which, tvOS 11’s big feature is Amazon Prime support, but that hasn’t been included in the developer betas yet. It also offers automatic light and dark mode switching, plus support for AirPlay 2 and AirPods.
The developer release of tvOS 11 beta 9 requires an Apple Developer account.
Thursday’s accelerates an already accelerated release cycle, as the last developer beta for tvOS 11 hit on Monday of this week. Apple is expected to ship tvOS 11 in September.