They turn iMessage on by default when you sign in because signing into your account and signing into iCloud purposefully conflated. Its very sneaky and arguably just as bad as the whole Microsoft local accounts lol.

To sign into your account locally and avoid iCloud, you have to sign in in the AppStore on both iOS and MacOS. Its fhe only way. On Mac, iCloud is activated by signing in the Settings place (same as iOS) or that Apple Media Account/Services they pester you with constantly.

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