I think you should use Flutter's official method for deep linking because third-party packages can get deprecated anytime, like in the case of Firebase deep linking. So, my suggestion is to rely on Flutter's official documentation.

I have explained a properly working deep link in an article with step-by-step details, which works on both Android and iOS.

https://trushitkasodiya.medium.com/flutter-deep-link-app-link-implementation-a-comprehensive-guide-for-2024-fb1418d998d1