the tires on the vehicle had a missing chunk of tread near the edge of the flat part of the tire and sidewall. It was obviously unsafe to drive. Carmax's reply was "you can buy it at the price we listed or return it but we're not repairing that tire. You can repair it yourself."

Friend returned the SUV to them and went to a regular dealer.

I've heard people have frustrating experience with Carvana but I do not know details.

I would expect that Carvana and Carmax are great ways to get cheap cars as-is, no negotiations.