Apple does not allow your iOS iCloud data to be encrypted in a manner where Apple cannot access it. As is alluded to in this article. Privacy advocates and privacy caring IT specialists have repeatedly asked Apple to offer such an option, but so far Apple has decided that regular people would turn such an option on, forget their password, then ask Apple for help and would be unhappy with their brand experience if App…
Just use different OS then
On mobile, the only realistic alternative is Android, which is a privacy and security nightmare.
On general purpose computers, Linux is better from the perspective of privacy. But for large parts of the general population, Windows is the only realistic alternative. And we know how important privacy is to Microsoft these days :(.