Answered: Follow-Up: Non-VEX LCDs

Original Q&A summary:
Non-VEX LCDs are legal provided they do not display anything related to the state of the robot.

Emphasis added by me.

Would it be correct to interpret <R7>d as prohibiting “functional” use of non-VEX LCDs only during matches and skills runs?

Or must non-VEX LCDs be limited to “nonfunctional” nature for the entirety of an event, including time in the pits and practice fields?

For example, would this be legal:
When the joystick is plugged in to field control, the non-VEX LCD is automatically put into a “nonfunctional” mode that displays only static images, non-robot-related animations, etc. When not plugged in to field control, the non-VEX LCD displays sensor data. A manual override would be used to put the non-VEX LCD into “nonfunctional” mode should the robot fail to do so automatically for a match or skills run.

Yes, this is correct.

Provided that no rules are violated in the process, this would be legal. However it will be up to you to prove that this LCD will not “affect the robot performance in any significant way or affect the outcome of the match”. I would be very cautious of trying this approach.