The Connecthings Flutter plugin allows you to access to the GDPR methods and In-App actions methods from the Dart code.
Nevertheless, the configuration of the SDK must still be done at the android and iOS app level.
A Flutter application is available on github to show you a concrete implementation.
You just have to clone the plugin repository https://github.com/herowio/herow-bridge-flutter, and open it with an android studio configured for flutter.
You can read the official Herow flutter plugin documentation at the following address https://pub.dev/packages/herow