Hello,
Apple published the Xcode beta6, but the stable version of Xcode16 has not been released in AppStore yet. (Xcode 16 Release Candidate)
Preview version is not supported on Q&A, you can refer to the GitHub issue to use preview Xcode: Figure out how to publish Xcode preview packages · Issue #18343 · xamarin/xamarin-macios (github.com)
If you have any other issues about the Xcode16 and iOS18 support, please rise an issue at GitHub.
Best Regards,
Wenyan Zhang
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