There is zero iCloud account requirement. You do not need to use the App Store. Gatekeeper can be disabled with a configuration profile key. Telemetry (what little there is) can be disabled with a configuration profile key. Siri can be disabled, all of the generative AI crap can be disabled, yadda yadda yadda, with a configuration profile key. Every background service can be listed and disabled if you disable authenticated-root. Hell, you could disable `apsd` and disable all push notifications too, which require a phone home to Apple.