@Jason This seems completely artificial that it's not supported to run an app from an older version of Xcode on a later iOS version. As you can build the app for device. Then go to Window > Devices and Simulators > Select your iPhone > Installed Apps > + > Navigate to DerivedData and find the app just built. And the old version of Xcode will happily install the app. I can somewhat understand not being able to debug and get logs though

In the terminal run: defaults write com.apple.dt.Xcode DVTEnableCoreDevice enabled Then restart Xcode 14 the iOS 17 device will show up in Xcode like below and you can run and debug the app as usual. (You may need to go to Devices and Simulators to pair/trust the device) I have Xcode 15 beta installed alongside Xcode 14, I'm not sure if that's required or not.

I also had having this issue with CocoaPods dependencies. I found the issue is with Explicitly Built modules not Xcode 26 specifically. It's just that Xcode 26 has explicitly built modules on by default. To work around it you can set Explicitly Built Modules to no. But I'm surprised not to find anyone else having issues with this in Xcode 16, nor any mention of explicitly build modules on CocoaPods. I know it's end of life but still. The real fix is to stop using CocoaPods.