It is VERY hard to turn off all this auto-Cloud backup stuff. Sometimes an OS update (undesired) can undo many key settings.
I tried to move over to a Linux OS phone (PinePhone), but the OS is still in Beta and shows it. It is quite slow, and advice on the web for finding a provider can be out of date, so finding a cell provider that doesn’t lock you into a fat contract can be challenging.
So, I cannot recommend the Linux phone at this time. Back to iOS.
The difference is Apple has already said they will scan your data and report to police for crimes they think are worth reporting.
Like you, I tried to use the Pine Phone (linux) but the software still remains too beta for daily use. I did nlt go back to iOS when they implemented on device scanning of photos or whatever else they want. I bought a pixel and installed GrapheneOS, a google-free hardened version of android. Graphene makes it easy to install from a webpage, or from the command line if you want.
If it’s a standards-compliant phone, you can just sign up for any pre-paid cell network that provides a SIM card. No lockin necessary.