I have a 2020 F350 Super Duty. I installed a lighted headache rack (tail, brake and turn signals)that I plugged into the flat 4 pin trailer towing bumper fitting. Everything worked fine but the truck thought there was a trailer attached so the back up assist didn't work. The blind spot detector worked OK by setting the trailer length to the minimum 3' setting. I tied installing a flat 4 pin spliced into the white/brown/ yellow/green wires leading to the factory 7 pin in the hopes that the headache rack lights would function without the truck thinking there was a trailer attached. The headache rack tail lights would come on but turn signals and brake lights don't work. What does it take to outsmart the truck?

 

You might be able to use a kit like the link below and wire splice into the vehicle lighting harness to provide a flat four trailer connector for your light rack.
This type of trailer wiring kit does not run off the vehicle lights power but rather uses them as a input, the power is provided by a constant 10amp fused power and ground wires. I dont know if this will work since the vehicle modules are getting so smart at finding a fault.

https://www.etrailer.com/Custom-Fit-...leID=200551567