I've been developing using Xcode (10.1) on an iMac (21.5-inch, Mid 2010) running macOS High Sierra (Version 10.13.6).
The last time I updated my app on the App Store, I got a warning:
ITMS-90725: SDK Version Issue – This app update was built with the iOS 12.1 SDK. As of June 30, 2020, updates to apps for iPhone or iPad must be built with the iOS 13 SDK or later.
I read that iOS 13 SDK comes bundled with Xcode 11.
But when I go to App Store → Updates, I don't see anything to update on my iMac. I can expose "1 incompatible Update", which is "Xcode Version 11.5", which should include iOS 13 SDK. This is what I would need in order to keep updating my app on the App Store, but it's "incompatible".
The problem seems to be confirmed by this compatibility chart. It looks like my current OS is as far as Apple is willing to take me on my current hardware (High Sierra, but not Mojave or Catalina).
My question is, is there any work-around that would allow me to use my current machine, but build using iOS 13 SDK?
I power-on this machine on three or four times per year, in order to make a tweak to the application, and then upload the new app to the App Store. I really don't need or want to buy another computer just to do this.
Best Answer
macOS High Sierra 10.13.6 is as far as your iMac can go and the last version of Xcode supported on this version of macOS is Xcode 10.1 which comes with iOS 12.1 SDK.
You can not install any app updates from the Mac App Store that have a minimum OS version number requirement that is later that the one you have installed.
Sadly no. It's not possible to run Xcode 11.x or later which includes the iOS 13.x SDK on macOS High Sierra 10.13.6.
Depending on your machine configuration, you may explore the possibility of running a virtual machine on your iMac that can then run macOS Mojave or macOS Catalina which in turn could run Xcode 11.x. That's the only way you can build an app with iOS 13 SDK and submit it on the App Store. But again that's neither a convenient or a future proof approach.
You can look into the possibility of renting a Mac temporarily, export your identity onto it, set it up for development, and build and submit your app update.
MacinCloud is an online cloud based Mac rental service that you can use for precisely this purpose. I have used the service in the past and found it to be satisfactory. Once you have set it up, you can start a screen sharing session to the computer and use it as you'd normally use a Mac. Check the linked website for more details.
P.S.: No affiliation with MacinCloud. Have used their services in the past and found them satisfactory.