Looks my graphics card (Nvidia GeForce GTX 560 Ti) has been moved to legacy status. However, the 390.xx legacy drivers are not available on NixOS yet:

"x86_64-linux"Linux 4.19.0, NixOS, 19.03pre156996.c70ad805d21 (Koi)yesyesnix-env (Nix) 2.1.3"nixos-19.03pre156996.c70ad805d21"""/nix/var/nix/profiles/per-user/root/channels/nixosWith https://github.com/NixOS/nixpkgs/pull/49703 you should be able to set
hardware.nvidia.package = config.boot.kernelPackages.nvidiaPackages.stable_390;
I have the same Problem as described in this issue, but simply adding
hardware.nvidia.package = config.boot.kernelPackages.nvidiaPackages.stable_390;
to my configuration.nix yields following error:
error: The option `hardware.nvidia.package' defined in `/etc/nixos/configuration.nix' does not exist.
I need more Information to set this up correctly. Can anybody help me?
Edit:
Nevermind. I didn't notice the referenced pull-request still being open.
Mind trying #51294 using nvidiaLegacy390 in videoDrivers though FRidh's solution should work.
I haven't done any development on nixos before, how would I test this?
I cloned your repo, but I don't know how to proceed from there.
You can build packages from the repository by using the -I parameter:
$ cd nixpkgs
$ nix-build -I nixpkgs=$(realpath .) -A linuxPackages.nvidia_x11_legacy304
$ sudo nixos-rebuild switch -I nixpkgs=$(realpath .)
For more ad-hoc questions, you can also join IRC.
According to the manual the following would load other nvidia packages:
services.xserver.videoDrivers = [ "nvidiaLegacy340" ];
services.xserver.videoDrivers = [ "nvidiaLegacy304" ];
https://nixos.org/nixos/manual/#sec-x11-graphics-cards-nvidia
@Mic92 Thank you for your help!
I have successfully built the package, installed, and loaded nvidiaLegacy390 via configuration.nix, and can confirm that #51294 does indeed solve my problem.
Most helpful comment
With https://github.com/NixOS/nixpkgs/pull/49703 you should be able to set