https://github.com/apple/swift-async-algorithms
Requires Xcode 14, which is still in beta and cannot push to the App Store.
Also, Apple fucked their back port badly. It’s supposedly fixed now, but if you built an app that used async/await anywhere in Xcode 13.X and a user installed running iOS 12/13/up to 14.5 they’d crash on launch.
So I personally wouldn’t trust it, and instead just push to raise your iOS minimum. I’ve had no problems requiring iOS15 in my projects over 1M installs