It could be nice to have the navbar of Android hidden.
UMG doesn’t scale based on it too, which is a bug I think.
This is coming soon. There is experimental support in 4.8 preview, but not exposed at the moment. In GameActivity.java, change this line:
private boolean ShouldHideUI = false;
to true. This turns on immersive sticky on KitKat and above. Eventually this will have a checkbox and runtime controls.