The iPad Pro 2018 has a single USB-C port. I have a dongle (USB-C => Audio) that lets me use headphones, I have a dongle (USB-C => USB-A) that lets me plug in a MIDI Keyboard.
What I want is to be able to do both.
Devices like this ought to be ideal but this one only lets power through the USB-C port.
There are also a number of large hubs, but they often have poor ratings related to the audio output quality.