Apple、デベロッパー向けにiOS 15.6 RC (19G69)、iPadOS 15.6 RC (19G69)、macOS 12.5 RC (21G69)、watchOS 8.7 RC (19U66)、tvOS
tvOS 15.6 RC (19M63)を配布開始
https://developer.apple.com/news/releases/