From the top result of searching online, but it's just one of many you can find easily enough: https://pwn-all.com/blog/2026/07/28/iphone-telemetry-in-2026-what-apple-knows-about-you.html
And that doesn't cover the data that gets processed and stored by servers rather than on device. Just like Google and most others, Apple holds all the encryption keys for the data at rest for "convenience". And this includes app backup data which would include encryption keys for any true end-tp-end encrypted services if you choose to backup that data to your account. Not going to speculate on whether or not they regularly use or sell that data, but they definitely give it to any government agencies or copyright enforcement agencies that properly request it.