My iPad Air 5 has a backlit combination keyboard/trackpad which makes connection to the iPad via the Smart Connector extension wiring in the internals of the case enclosing the iPad. Strong magnets align and retain the keyboard in place. If I connect the keyboard while the iPad is locked, up pops this message: “Unlock to use USB devices.” This tells me there are two USB interfaces on this iPad: the three-terminal Smart Connector and the USB-C power/sync connector.