This repo contains a universal solution for reporting SwiftUI animation status (started, finished) using the method of checking the trail of 3 adjacent keyframes, which works with spring animations. (The repo is planned to be being extended in the future.)
While the lowest platforms this method works on are iOS 14 and MacOS 12, I decided to stick to the most recent versions of them since this repo is more of a lab work on functionality that is still evolving, rather than being a stable library repo.
There's also an article for this method SwiftUI Spring Animation Completion Tracker.
An iOS app demonstrating the use of this view modifier: AnimationStatusReporterDemo.