I have a 2021 Chevy Express 2500 Cargo standard length. It did not come with a tow package. Is there a factory plug in the back somewhere that I can use to install a 7way trailer plug? Also is there one under the dash for a brake controller? Thank you for your assistance.

 

I had to run all new wiring for the controller and the plug on my 2015.
The trailer plug is fairly easy to do with an adapter kit for the lights. For the brake control and 12 volt line I ran blue, and red 10 gauge wires from under the hood to a rear bumper terminal box. Black #10 for the ground attached from the rear frame to the box.
The controller plug is slightly more complicated. For a brake signal I had to tap into the center rear brake light wire. I also added a small fuse panel under the hood for the brake controller.
GM has different fuse boxes for the trailer package. The wiring may or not be present depending on options but if you don't have the trailer package the fuse box terminals for trailer towing are missing.

This is the biggest hitch I could find. Bought it and the light kit adapter from eTrailer

https://www.etrailer.com/Trailer-Par...AaAp4rEALw_wcB

 

Short answer, no, I looked for days and many forums. No. But the kits are reasonably easy to use. If you need details I installed one from scratch for my 2021 3500 extended.