Xcode 12.1 GM Seed 1 was released on 13 Oct 2020 and requires macOS 10.15.4+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_12.1_GM_seed/Xcode_12.1_GM_seed.xip.
Release notes are located at https://developer.apple.com/documentation/xcode-release-notes/xcode-12_1-release-notes.
The SDKs it contains are:
- iOS 14.1 (Build 18A8394)
- macOS 10.15.6 (Build 19G68)
- tvOS 14.0 (Build 18J390)
- watchOS 7.0 (Build 18R382)
The compilers it contains are:
- clang 12.0.0 (Build 1200.0.32.21)
- swift 5.3 (Build 1200.0.29.2)