@sycophantic oh, I guess I could have just gone straight to their documentation!
https://documentation.rossvideo.com/files/Manuals/CG%20and%20Graphics/XPression/Hardware%20Specs/XPression%20Custom%20Keyboard%20Specs.pdf
it looks like at least now, they come with an attached USB cord - which probably lands right on that unpopulated header I found next to the rj45.