So I can finally post! Thought I'd make my first one useful. I spent forever googling and coming over posts in here trying to find out how to use the factory backup camera with my Pioneer double din head unit, to no avail with my particular radio (non-JBL 2018 Off Road Premium, Stock HU is the Panasonic 86100-35362)
(this one)
Here's the back:
Traced the camera power (to) and signal (from) back to this plug with 4 wires (6V+ is Red, 6V- is Orange):
rather than frying anything, searched extensively and found this adapter (model UX-TY002), prayed it would work given it didn't list the 2018 runner in the applicable vehicles (it did)
Traced the reverse signal hot to this wire (red one under my finger, second from the top left in this plug)
which is 12v and the factory deck does in fact put out 6 volts, but a 12v-6v transformer comes with the UX-TY002 so you're good.
Wired that reverse hot to the camera power + and to the aftermarket HU lead for reverse input, and the grounds for each to the common ground in the harness. I also bought the AntennaWorks 40-LX11 antenna adapter which worked great- shown with blue wire (not used) on left
And it works like a champ! Hope this helps someone avoid some of my same hours of frustration.