1. apt -t ascii-backports install xserver-xorg-video-nvidia
  2. Reading package lists... Done
  3. Building dependency tree
  4. Reading state information... Done
  5. Some packages could not be installed. This may mean that you have
  6. requested an impossible situation or if you are using the unstable
  7. distribution that some required packages have not yet been created
  8. or been moved out of Incoming.
  9. The following information may help to resolve the situation:
  11. The following packages have unmet dependencies:
  12. xserver-xorg-video-nvidia : PreDepends: nvidia-installer-cleanup but it is not
  13. installable
  14. PreDepends: nvidia-legacy-check (>= 343) but it is
  15. not going to be installed
  16. Depends: nvidia-alternative (= 418.74-1~bpo9+1) but it is not going to be installed
  17. Depends: nvidia-support but it is not installable
  18. E: Unable to correct problems, you have held broken packages.

apt -t ascii-backports install xserver-xorg-video-nvidia