As native developers might know. Android still has the option for a buttons navigation bar with a back button that cannot be bound to a nanoflow or caught in some other way by Mendix because it's handled natively.
We have used a marketplace widget to catch this action and handle it for the past time. But recently this widget started throwing errors because the method is deprecated.
We are now developing our own widget, this is done relatively simple with some JS code but we are hoping this could become a platform supported widget or base Mendix option. It's widely used in apps because during some operations you don't want to accidentally lose uncommited data, need to rollback some actions, want to save data for later or simply just block the back button entirely.