Connecting a MIDI Keyboard to an iPhone XS Max! 2019 - YouTube
Connecting USB Keyboard/Piano to iPhone & iPad for Recording in GarageBand iOS - YouTube
Amazon.com: Lightning to MIDI Cable for iPad/iPhone, [Apple MFi Certified] USB - B Midi Cord for Midi Controller, Electronic Music Instrument, Piano, Midi Keyboard, Recording Audio Interface, USB Microphone : Musical Instruments