Xcode 12.0 Beta 3 was released on 22 Jul 2020 and requires macOS 10.15.4+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_12_beta_3/Xcode_12_beta_3.xip.
Release notes are located at https://developer.apple.com/documentation/xcode-release-notes/xcode-12-beta-release-notes.
The SDKs it contains are:
- iOS 14.0 (Build 18A5332e)
- macOS 11.0 (Build 20A5323l)
- tvOS 14.0 (Build 18J5344e)
- watchOS 7.0 (Build 18R5340d)
The compilers it contains are:
- clang 12.0.0 (Build 1200.0.26.2)
- swift 5.3 (Build 1200.0.22.4)