Add basic config for networkd.

config/networking.nix

@@ -1,7 +1,42 @@
-{ config, ... }:
+{ config, lib, ... }:
+
+with lib;
 
 {
   networking = {
     hostName = config.machine.hostName;
+    useNetworkd = config.machine.useNetworkd;
+    useDHCP = !config.machine.useNetworkd;
+    dhcpcd.enable = !config.machine.useNetworkd;
   };
+  # Based on
+  # https://github.com/NixOS/nixpkgs/issues/10001#issuecomment-905532069
+  systemd.network = mkIf config.machine.useNetworkd {
+    enable = true;
+    networks = let
+      networkConfig = {
+        DHCP = "yes";
+        DNSSEC = "yes";
+        DNSOverTLS = "yes";
+        DNS = [ "1.1.1.1" "1.0.0.1" ];
+      };
+    in {
+      "40-wired" = {
+        enable = true;
+        name = "en*";
+        dhcpV4Config.RouteMetric = 2048;
+        inherit networkConfig;
+      };
+      "40-wireless" = {
+        enable = true;
+        name = "wl*";
+        dhcpV4Config.RouteMetric = 1024;
+        inherit networkConfig;
+      };
+    };
+  };
+  # Wait for any interface to become available, not for all
+  systemd.services."systemd-networkd-wait-online".serviceConfig.ExecStart = [
+    "" "${config.systemd.package}/lib/systemd/systemd-networkd-wait-online --any"
+  ];
 }

options/machine.nix

@@ -59,6 +59,13 @@ in {
         The Machines HostName
       '';
     };
+    useNetworkd = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Disables dhcpcd and enables networkd.
+      '';
+    };
     binaryCaches = mkOption {
       type = types.listOf types.str;
       default = [];