iCloud seems peerless from a privacy standpoint.

I haven’t seen this mentioned much on HN (perhaps because it’s relatively new, an opt-in feature, and not open-source), but iCloud offers E2EE for most of its services. Of course, one has to implicitly trust Apple’s implementation as I don’t believe this is auditable by independent sources. Would love somebody more knowledgeable than me in this topic chiming in!