Is it possible to enhance U-boot such that (or does it already support) it presents as USB CDC class peripheral, so that standard OS drivers can connect, and get to the boot console that way?
This has the disadvantage that you probably can't attach to the console until after boot is underway, so it may not be worth pursuing, but I was curious.
I'm thinking of making a new Beaglebone Black variant with USB-C support built in (primarily for power). I think I'll just include some kind of FTDI chip on board.