What's the cutoff? If you have a single user who's running iOS 7 and you have to slow down feature development 50% to support them, do you have to do that out of respect?
You should at least support what the latest devices support, e.g. iPhone 12 mini with Display Zoom turned on and large fonts. Incidentally, that will also mostly take care of the iPhone 5/5S/SE1 screen size.
https://hacknicity.medium.com/how-ios-apps-adapt-to-the-vari...