Sorry I am late replying. I was in the market for a phone, not an OS. I have no interest in learning and maintaining the skillset needed to change the OS on my phone.

I need a phone with robust support and good warranty. At the time I bought my iPhone 10S, it was a good choice, and I could even buy it locally to me. I was unaware of any option that would offer those things, was generally available, and didn't run Android (with Google Apps) or iOS.

iOS is a closed platform, but this is the only obvious negative thing about it, privacy-wise. You can opt out of every single cloud thing that ships with the phone, and most are even opt-in (for example, iCloud and Apple accounts in general). The phone ships with a robust suite of productivity apps, a modern web browser that is kept up to date, and many privacy options. And usually, opting out of something doesn't break some other random other feature on the phone for no reason. (I recently saw a recording of how you cannot have Google search installed on Android and refuse to share your call logs with it. Why? There are no such restrictions on anything on iOS, as far as I have found.)

The UI layer is closed source in Sailfish OS, so not better than iPhone in this case.

For Android, if getting a Lineage OS in phone, the first problem is Lineage OS still does not have automatic update without manually reboot into recovery mode, and need for user invention. Let's be honest I don't bother to update because of requiring human intervention in update until I find the time to do it. Not a good practice but hey...

Secondly, any phone could be dropped support by Lineage OS if the developer of that model just starts using another phone and cannot find another to continue supporting the phone.

The best option for privacy seems to be using GrapheneOS with Pixel phones, but GrapheneOS only supports as long as the support cycle of a pixel phone, so it is 3 years before end-of-life minus the time to develop GrapheneOS ROM for a new pixel phone. If you are going to value your privacy so much then this is the best, but a quite expensive route and not really environmental friendly.

An iPhone can receive update as long as Apple the company is not bankrupted. Well, you get a worse performance after update but at least it is an option to continue to use.