I read that: "Starting April, 2020, all iPhone and iPad apps submitted to the App Store will need to be built with the iOS 13 SDK or later."
I have an app that's build with Xcode 10.3, until when can I use Xcode 10.3 to update the app?
Midnight April 19, PST would be my guess. I wouldn't push it tho.
That said, remember, there is a difference between building with a given version of Xcode, and submitting with a given version. As well, there is a difference between updating an existing app, and submitting a new app.
This is a quote from the docs, that while years old, might still apply...you'd need to test to confirm, tho:
"For compatibility reasons, the App Store will often accept apps that are built with some older versions of Xcode or Base SDK.
To determine if an older Xcode configuration is currently accepted by the App Store, you can choose "Archive" under the "Product" menu to make an archived build, then use the Validate feature, to test if that build meets minimum requirements for submission to the App Store."
Finally, don't forget that Xcode is not the lone method of uploading to the store - see the docs on Transporter (requires macOS 10.13 or later BTW) if you are not already familiar.
Good luck.
