Dated Sept 12:
Only realized this now, RC is not a Beta.
Build your apps and games using the Xcode 15 Release Candidate and latest SDKs, test them using TestFlight, and submit them for review to the App Store.
https://developer.apple.com/news/?id=khzvxn8a
So looking at the download pages:
Xcode 15 Release Candidate
Xcode 15 RC enables you to develop, test, and distribute apps for Apple platforms. It supports the SDKs for iOS 17, iPadOS 17, tvOS 17, watchOS 10, and macOS 14. For development with the visionOS SDK, continue to use Xcode 15 beta 8.
https://developer.apple.com/download/applications/
NOTE: the website menu still says "Xcode 15 Beta", which isn't entirely inaccurate, since beta 8 is still out there.
MQTest
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution