On a EK-TM4C1294XL Rev D board the U6 External debug connector is not polarized, and thus can plug in a cable in either the correct or incorrect orientation. There is no indication of which is pin 1 on either the silkscreen or User's Manual SPMU365A.
For reference, the red arrow below points to pin 1:
Perhaps the User's Manual can be updated to add this information.
