Designed for the fourth and fifth-generation Apple TV models, the tvOS 11.3 developer beta can be downloaded onto the Apple TV via a profile that's installed using Xcode.
According to Apple's release notes, tvOS 11.3 includes bug fixes, new features, and security improvements, with a list available below:
- Enhancements to Match Content support.
- Automatic frame rate switching on Apple TV 4th Generation.
- Automatic mode switching for AirPlay video sessions.
tvOS 11.2.5, the previous tvOS update, featured no major outward-facing changes that were noticed by Apple TV users, appearing to instead include minor under-the-hood updates.