If you want to get firebase dynamic link if app is already running in flutter? I had the same problem and I solved using WidgetsBindingObserver to listen when the app is foreground, but I found an issue on iOS.
Diego Velasquez has wrote a post about it, you can check it:
https://medium.com/@diegoveloper/flutter-firebase-dynamic-link-6f1b79278ce0
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