How to use / configure Android mobile app to use custom OAuth login

We have configured our Rocket Chat to use a custom OAuth provider. We have a custom login button for the website/windows app to use, but how do we get the mobile app to display the custom OAuth login button. We are not using the built in RocketChat login process and since the mobile apps do not show the custom login button, the mobile app is not much use to us. Are we simply missing a config in RocketChat mobile.

We are using Android version 4.6.4.2118

Thanks
Paul