Fully power down an Nvidia dGPU when its not in use

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Hi, I’m an Arch Linux user and recently I wanted to try out NixOS. I have an Nvidia Optimus laptop (Dell XPS 15 9570) with a GTX 1050 Ti. When I was using Arch I could fully disable/reenable the GPU without the need to reboot or log out by following [the instructions on the Arch Wiki].(Dell XPS 15 (9570) - ArchWiki).

I’ve tried to replicate that setup on NixOS, here’s what I added to my configuration.nix file:

  hardware.opengl = {
    enable = true;
    driSupport = true;
    driSupport32Bit = true;
  };

  nixpkgs.config.allowUnfreePredicate = pkg:
    builtins.elem (lib.getName pkg) [
      "nvidia-x11"
      "nvidia-settings"
    ];

  services.xserver.videoDrivers = lib.mkDefault ["intel" "nvidia"];

  hardware.nvidia = {
    modesetting.enable = true;
    nvidiaSettings = true;
  };

  hardware.nvidia.prime = {
    offload = {
      enable = true;
      enableOffloadCmd = true;
    };

    intelBusId = "PCI:0:2:0";
    nvidiaBusId = "PCI:1:0:0";
  };

  boot.blacklistedKernelModules = [
    "nouveau"
    "nv"
    "rivafb"
    "nvidiafb"
    "rivatv"
    "nvidia"
    "nvidia-drm"
    "nvidia-modeset"
    "nvidia-uvm"
    "ipmi_msghandler"
    "ipmi_devintf"
  ];

  systemd.services.disable-nvidia-on-shutdown = {
    enable = true;
    description = "Disables Nvidia GPU on OS shutdown";

    unitConfig = {
      Type = "oneshot";
      RemainAfterExit = true;
    };

    serviceConfig = {
      ExecStart = "${pkgs.coreutils}/bin/true";
      ExecStop =
        ''
          /bin/sh -c "mv /etc/modprobe.d/disable-nvidia.conf.disable /etc/modprobe.d/disable-nvidia.conf || true"
	'';
    };

    wantedBy = ["multi-user.target"];
  };

I’ve also created the /etc/modprobe.d/disable-nvidia.conf file as in the Arch wiki, since I don’t know how to do it the “Nix” way yet.

My laptop boots up without the Nvidia GPU running - lsmod | grep nvidia returns nothing and its power usage is low. I can turn the GPU on by using the enableGPU.sh script from the Arch Wiki (its fans start spinning) but lsmod | grep nvidia returns nothing. I can also turn the GPU off accordingly. When the GPU is turned on, the nvidia-offload script from the NixOS Wiki doesn’t do anything. None of my programs can see the Nvidia GPU (I’ve tried Blender, glxinfo, and Dolphin Emulator).

How should I do this properly?