After installing launch_at_login by adding to the pubspec.yaml and running flutter pub get -v

It will return the path of the launch_at_login lib (something like: ~/.pub-cache/hosted/ in which there will be an assets folder with a file called

Add to your macos Xcode project in the Build Phases -> Run Script:

/bin/sh ~/.pub-cache/hosted/

this builds the helper app to launch your MacOS app on login.

Then you can run:

$ flutter run -d macos