Only the USB-C Apple Pencil works with the iPhone Duo, MacRumors reports
Only one Apple Pencil works with the iPhone Duo, and it is the cheapest of the lot. According to a MacRumors hands-on, the USB-C Apple Pencil is the sole model supported by Apple's new foldable, while the Apple Pencil (1st generation), Apple Pencil (2nd generation) and Apple Pencil Pro are all incompatible, even though they work with iPads.
MacRumors reports that the USB-C Apple Pencil sells for $79 from Apple and can be found for around $69 at Amazon. Unlike the Apple Pencil Pro, which pairs magnetically with an iPad, the USB-C model has to be connected to the iPhone Duo with a USB-C cable to pair. The report adds that Pencil support arrives with iOS 27.2, which is currently in beta.