Debugging a different issue I found that network images were failing to load/display only in release mode for android.

Using a fresh flutter create and modifying the body to

body: Image.network('https://picsum.photos/250?image=9'),

Which is the example image given in https://docs.flutter.dev/cookbook/images/network-image