iPadOS 13 beta 8
UIPrinterInteractionController presents as a dismissible page sheet, with no option analagous to UIViewController's modalInPresentation property, nor it seems any way to set a different UIModalPresentationStyle value.
In iOS 13, page sheets can be dismissed by flicking them off the screen.
When the AirPrint page is flicked off the screen, the underlying app no longer responds to any input and has to be closed to recover.
Filed as FB7287401.