So here is what I did:
I installed this:. CURT Custom 4-Flat Select Mitsubishi Outlander PHEV OEM. The connector fit perfectly in the connector that is under the rear left cover in the back trunk or boot. The connections were not the same so I had to change the pin configuration, but that was quick and easy.
And I installed this: Super repairman 4-Way Flat to 7-Way RV Round Blade and 4 Way Trailer Wiring Harness Adapter Trailer-Side 7 Pin and 4 Pin Dual-Output Connector Kit with Mounting Bracket. Now I have both connections for trailers of any type.
Then I installed this on a trailer: Tekonsha 902502 Prodigy RF, Plug & Play Trailer Mounted Proportional Brake Controller for Trailers with 1-3 Axles, Black. And this can be easily installed on any trailer you want to pull behind the car.
To set up works super and fully adjustable with any size or weight trailer.
It shouldn't interfere with the warranty because I am not installing a trailer brake system changing any of the wiring or connections of the vehicle since the actual trailer brake controller is on the trailer and not part of the car.
All done DIY, simple, under $400 for everything and no changes to the car.
Hope this helps