Failed to find assets path for "Frameworks/App.framework/flutter_assets"

I've just managed to solve this issue. I've just followed advise https://github.com/flutter/flutter/issues/29974 and added "$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" embed to Run script Run script After rebuilding App.framework folder has been added to build directory and problem has gone. Hope this will help someone else.

You can follow the instructions in https://flutter.dev/docs/development/ios-project-migration

Particularly the build phase:

/bin/sh "$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" embed
/bin/sh "$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" thin

You can see more here: https://github.com/flutter/flutter/issues/52084#issuecomment-600768772