https://wccftech.com/usb-c-port-on-magic-keyboard-for-ipad-pro-is-for-charging-only/

Before you get excited that you will be plugging USB drives into it, the new Magic Keyboard's USB-C port is for charging the iPad Pro only.

Probably the most surprising announcement today was the Magic Keyboard for the new 2020 iPad Pro. Rather than going ahead with the known origami style keyboard, Apple went 'screw it' and decided to make the iPad Pro float and use physics to keep everything upright. With that design choice, Apple appeased users by adding a USB-C port into the keyboard's hinge. While most of you think that it's a fully capable port, let me break your heart right now and tell you that it is not.