Not possible right now, or to be more precise, when you specify the “app group” or “team” for notifications, that can include Org Groups too, but you can’t specify an Org group directly.
For example, if you add your “QA” org group to the app as “Testers”, then you can specify “testers” to be notified, but that will of course include everyone who’s a “tester” of the app, not just the “QA” org group.
If that’s not enough, feel free to create a Feature Requests, I’m sure this would be useful for others too!