I updated my iPhone to iOS 15.0 yesterday and I wanted to build in Xcode (version 12.5.1). But in Xcode it is showing 'iPhone (unsupported OS version)' and when I try to build (command + R) then I get the error:
Xcode doesn’t support iPhone’s iOS 15.0 (19A346).
Is there a way to use it without downgrading iOS?
Without updating Xcode, you need to put the relevant device file in the DeviceSupport section and run Xcode again. DeviceSupport files are located here.
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport
https://github.com/filsv/iPhoneOSDeviceSupport
You can download iOS15 devicesupport file from here, then you need to unzip, then you need to put it in DeviceSupport section on your mac.
When you restart Xcode, there should be no problem.
Update for iOS 15.1
For 15.1 devices, You can copy file from 15.0 to the same directory as 15.1. Then you need to open Xcode again, it should be fine.