Not sure about the 2021 model year but on my 2020 with the factory tow package the wiring was there under the dash, it just had to be spliced and connected to the controller. I had the dealership where I bought mine at new install the one Ford offers and they said they didn't have to do anything with the headliner but I didn't watch them install it and it doesn't look like they messed with it. The reason I went with that one verses one from another source is that one has an extra module for the AEB system. If I went with the one from another source it doesn't have that module so if the AEB activated while towing it would not apply the trailer brakes which could be a disaster and I didn't want to mess with having to remember to turn the AEB off when towing. So far it has been working fine and thankfully I haven't been in a situation where the AEB was activated

 

Thank you so much for your response. I haven’t approached my dealership yet. Next oil change I am going to discuss with them.

 

I have a 1994 Ranger that I am installing a kit from etrailer, I have all the wires run all I have to do now is pull the dash and hook the controller up.