Replace light with brightnessctl

modules/gui.nix

@@ -40,6 +40,7 @@ with pkgs;
       qt5.qtwayland
       glib
       udiskie
+      brightnessctl
     ];
     extraSessionCommands = ''
       export MOZ_ENABLE_WAYLAND=1
@@ -57,9 +58,6 @@ with pkgs;
     wrapperFeatures.gtk = true;
   };
 
-  # Backlight
-  programs.light.enable = true;
-
   # Blue light filter
   location.provider = "geoclue2";