Sure!

App flake.nix:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
  };
  outputs = {nixpkgs, ...}: let
    pkgs = import nixpkgs {system = "x86_64-linux";};
  in {
    packages.x86_64-linux = {
      default = nixpkgs.legacyPackages.${"x86_64-linux"}.callPackage ./nix/package.nix {inherit pkgs;};
      devShells.default = import ./nix/shell.nix;
    };
    nixosModules.default = import ./nix/module.nix;
  };
}

package.nix:

{
  lib,
  pkgs,
}: let
  cargoTomlPath = ../Cargo.toml;
  cargoTomlContent = builtins.fromTOML (builtins.readFile cargoTomlPath);
in
  pkgs.rustPlatform.buildRustPackage rec {
    pname = "oblichey";
    version = cargoTomlContent.workspace.package.version;
    src = lib.cleanSource ../.;
    cargoToml = cargoTomlPath;
    cargoLock = {
      lockFile = ../Cargo.lock;
      outputHashes = {
        "burn-0.14.0" = "sha256-ChBlLKeq0WuINP+6mfZ0vFMYOKWnqT2dEMuM0UZJnbc=";
        "cubecl-0.1.1" = "sha256-tLNC2KRRYrRRKL9HkhTYHg8tvxkJDm9fM8GrSQWNXeM=";
      };
    };
    nativeBuildInputs = with pkgs; [
      clang
      fontconfig
      pkg-config
      libxkbcommon
      libGL
      cmake

      wayland

      xorg.libXcursor
      xorg.libXrandr
      xorg.libXi
      xorg.libX11

      vulkan-headers
      vulkan-loader

      rustfmt
    ];
    buildInputs = with pkgs; [
      fontconfig
      vulkan-headers
      vulkan-loader
      pam
    ];
    preInstall = ''
      mkdir -p $out/bin
      cp -r target/x86_64-unknown-linux-gnu/release/weights $out/bin/weights
    '';
    postFixup = ''
      patchelf --add-rpath ${with pkgs; lib.makeLibraryPath [libGL libxkbcommon wayland vulkan-loader vulkan-headers]}/lib $out/bin/oblichey-cli
    '';
    LIBCLANG_PATH = "${pkgs.libclang.lib}/lib";
    LD_LIBRARY_PATH = "${pkgs.lib.makeLibraryPath buildInputs}";
  }

My system flake.nix:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    oblichey.url = "git+file:///home/simon/GIT/Rust/oblichey";
	...
  };
  outputs = {
    nixpkgs,
    hyprland,
    ...
  } @ inputs: {
    nixosConfigurations = {
      "TuxedoInfinityBook14Gen8" = nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";
        specialArgs.inputs = inputs;
        modules = [./nixos/machines/TuxedoInfinityBook14Gen8/system.nix];
      };
      ...
    };
  };
}

./nixos/machines/TuxedoInfinityBook14Gen8/system.nix:

{
  config,
  lib,
  pkgs,
  modulesPath,
  inputs,
  ...
}: {
  imports = [
    ../../system.nix
    (modulesPath + "/installer/scan/not-detected.nix")
    inputs.oblichey.nixosModules.default
    ...
  ];
  programs.oblichey = {
    enable = true;
    settings = {
      camera = {
        path = "/dev/video2";
      };
    };
  };
  ...
}

{
  lib,
  config,
  pkgs,
  ...
}: let
  cfg = config.programs.oblichey;
in
  with lib; {
    options.programs.oblichey = {
      enable = mkEnableOption "oblichey";
      package = mkOption {
        type = types.package;
        default = pkgs.callPackage ./package.nix {};
        description = ''
          The oblichey package to use.
        '';
      };
      settings = {
        camera = {
          path = mkOption {
            type = types.str;
            description = "Path to the IR camera to be used.";
          };
        };
      };
    };
    config = mkIf cfg.enable {
      environment.etc."oblichey.toml".text = ''
        [camera]
        path=${cfg.settings.camera.path}
      '';
    };
  }

In reply to @samasaur:matrix.org
I think the real fix is running nix flake lock --update-input nixpkgs in your nixos config

In reply to @blitz:chat.x86.lol
The quick fix would be in your NixOS config to manually set the package option of this module to the package output of the flake