Bummer that you're having these issues. However, my aftermarket brake controller was pretty much plug & play and works great w/o any additional software from the dealer.
I believe that the software from the dealer allows the vehicle to accept the OEM brake controller and integrates the OEM controller with the vehicle's software - including additional pages on the dash & possibly the infotainment screen. After-market controllers will not integrate with the vehicle software even if the additional software is installed. I went through this on my previous vehicle - a 2018 RAM 1500.
I also have the connector under the dash with the small plastic “male” part that unclips. Did you reuse that or buy an adapter to fit? I don’t get the point of the little plastic bit that seems like it should have factory female spade connectors but doesn’t. Any hints? Thank you!!