2014 Yukon XL here and am in the same boat. CANNOT locate the module in the kick panel! Anyone have a guess as to where it would be on these Yukons? Connect directly at the mirror/monitor and run RCA the entire way? Or trace the wiring by removing the A-pillar cover?
If I'm lucky enough to find the module, I found this harness to avoid having to even t-tap the wires!
https://camera-source.com/accessories/wiring-kits/2009-2013-silverado-sierra-split-mirror-and-navi-display-without-power-rear-window.html