Replace nouveau with the Nvidia driver

If a fresh install boots into the nouveau driver, swap it for the proprietary Nvidia one.

ubuntu-drivers devices

# Install the recommended driver:
sudo ubuntu-drivers autoinstall

# OR, pin a specific version from the previous output, e.g.:
# sudo apt install nvidia-driver-535

sudo reboot

After reboot, verify:

nvidia-smi
lsmod | grep nouveau   # should print nothing