And this can make the application entirely unusable for some users. I'm thinking in particular about accessibility for blind users, who need to use a screen reader, though other disabilities are also impacted. Basically, to be accessible, an application's UI components need to implement the platforms' accessibility APIs. Most non-native widgets don't do this, because it's a lot of work that most developers just don't even think about. As far as I can tell from a quick scan of the source, that currently includes Kivy. So beware that if you use Kivy and its non-native widgets, you'll be locking some users, admittedly a small minority, out of your app. Probably OK for a game; not so much for an application that's going to be used in a job or education.