replace networkmanager with systemd-networkd (again)

hosts/skipper/network/default.nix

@@ -7,6 +7,78 @@
     fallbackDns = [ ];
   };
 
+  systemd = {
+    network = {
+      enable = true;
+      wait-online.enable = true;
+      networks = {
+        "20-virbr" = {
+          matchConfig = {
+            Name = "virbr*";
+            Type = "bridge";
+          };
+          linkConfig = {
+            Unmanaged = true;
+          };
+        };
+        "21-docker" = {
+          matchConfig = {
+            Name = "docker*";
+            Type = "bridge";
+          };
+          linkConfig = {
+            Unmanaged = true;
+          };
+        };
+        "22-veth" = {
+          matchConfig = {
+            Name = "veth*";
+            Type = "ether";
+          };
+          linkConfig = {
+            Unmanaged = true;
+          };
+        };
+        "40-ether" = {
+          enable = true;
+          matchConfig = {
+            Type = "ether";
+          };
+          networkConfig = {
+            DHCP = "yes";
+          };
+          dhcpV4Config = {
+            UseDomains = true;
+            RouteMetric = 100;
+          };
+          ipv6AcceptRAConfig = {
+            RouteMetric = 100;
+          };
+        };
+        "40-wireless" = {
+          enable = true;
+          matchConfig = {
+            Type = "wlan";
+          };
+          networkConfig = {
+            DHCP = "yes";
+            IgnoreCarrierLoss = "3s";
+          };
+          dhcpV4Config = {
+            UseDomains = true;
+            RouteMetric = 600;
+          };
+          ipv6AcceptRAConfig = {
+            RouteMetric = 600;
+          };
+          linkConfig = {
+            RequiredForOnline = "routable";
+          };
+        };
+      };
+    };
+  };
+
   networking = {
     nameservers = [
       "10.10.10.1"
@@ -34,16 +106,6 @@
       ];
     };
 
-    networkmanager = {
-      enable = true;
-      dhcp = "dhcpcd";
-      dns = "systemd-resolved";
-      wifi = {
-        backend = "iwd";
-        powersave = false;
-      };
-    };
-
     wireless.iwd = {
       enable = true;
       settings = {