The next version of Steam Link for iOS and Apple TV is now available as a beta build.

You can opt into the beta on TestFlight by clicking on the link here:
https://testflight.apple.com/join/Cye7Gfyy

New in this build:

• Added Indonesian language support
  
• Added support for HDR streaming from Windows, requires selecting an enhanced 1080p/4K streaming configuration
  
• Fixed the Nintendo Switch Pro controller when connected to the latest Steam client