Swift 5.5 introduced Concurrency, a structured method of writing asynchronous code in a way that is extremely readable, and avoids many categories of potential bugs.

While language support is provided by the compiler, runtime support is currently provided by the OS libraries, which makes this addition unavailable for developers that support multiple OS versions.

The head of Languages & Runtimes at Apple, Ted Kremenek, has stated that the possibility of a backport is being explored.

We believe that such a backport is essential to all developers. Its existence would save millions of person-hours and eliminate many bugs.

While many of us support older iOS versions going back as far as 10 or 11, a backport to at least 13 will cover a sizable majority of all iOS users out there.

We as developers love to adopt new features that make our lives easier and enable us to ship great apps to users. That said, I personally have not been able to use SwiftUI (which came out 2 years ago) because I knew I won't be able to ship the app with it, since I have to support iOS 12.

This must not happen with Swift Concurrency, an idea much more universal than a UI framework.