install plasma and use plasma-manager to configure

home/plasma.nix

@@ -0,0 +1,25 @@
+{ ... }:
+{
+  programs.plasma = {
+    enable = true;
+    workspace = {
+      lookAndFeel = "org.ide.breezedark.desktop";
+      cursor = {
+        theme = "Bibata-Modern-Classic";
+        size = 32;
+      };
+    };
+
+    fonts = {
+      general = {
+        family = "IBM Plex Mono";
+        pointSize = 12;
+      };
+    };
+
+    input.keyboard = {
+      numlockOnStartup = "on";
+      options = [ "ctrl:nocaps" ];
+    };
+  };
+}