Apple has seeded the first developer betas of macOS Sequoia 15.6, iOS 18.6, iPadOS 18.6, , tvOS 18.6, watchOS 11.6, and visionOS 2.6. And, yes, these are separate from the developer betas for the “26 versions” of the operating systems previewed at last week’s Worldwide Developer Conference.
Registered developers can download the betas via Apple’s developer portal. Or they can be downloaded over-the-air once the proper configuration profile has been installed from the Developer Center.