on the upside, you can make a .mobileconfig that disables most of the apple cloud service shit for macOS, like music/icloud/appstore/etc. here's one:
https://git.eeqj.de/sneak/pub/src/branch/master/sneak/disable-apple-apps.mobileconfig
you can't configure IMAP email on macOS mail any longer without it phoning home to apple when you do so. i haven't inspected the traffic or binaries that do so, but if you want to configure imap email manually (or import a profile that does so) while blocking all communication to apple/icloud servers, macOS Mail.app won't work.
(edit: it works when installing via a profile, but only after some timeout/delay.)
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