biomurph

You are right, the Teensy D+ and D- pins will not do anything but USB 2.0. I will not argue with you about that. Other pins on the Teensy, however, can interface to some degree, more or less, with the alternate functionality in USB-C.

@jmarsh Actually, you're not correct in this instance. If I change the port on the Teensy side (UFP) to a USB-C, then I am able to connect to any USB-C DFP. With the right pullups and/or pulldowns on the proper USB-C port pins, I can tell the DFP...