Problem: My NVIDIA GeForce GT 710 is utterly broken under nouveau (artifacts so bad text does not render). Most forum posts that I found wanted to change llvmpipe to nvidia driver... That was the opposite of what I wanted. I don't want to install proprietary drivers. My display-server does not start without modesetting support.
Solution: Disable nouveau acceleration.
You can test it by using the kernel parameter nouveau.noaccel=1
.