tmpfsOnTmpfs true on bemmer

use settings attribute

hosts/bemmer/configuration.nix

@@ -30,6 +30,7 @@
 
   nixpkgs.system = "aarch64-linux";
   hardware.raspberry-pi."4".fkms-3d.enable = true;
+  boot.tmpOnTmpfs = true; # building stuff on sd-card is slow
 
   system.stateVersion = "21.05";
 }

shared-services/spotifyd.nix

@@ -1,12 +1,10 @@
-{ ... }:
+{ config, ... }:
 
 {
   services.spotifyd = {
     enable = true;
-    config = ''
-      zeroconf_port = 18572
-    '';
+    settings.zeroconf_port = 18572;
   };
 
-  networking.firewall.allowedTCPPorts = [ 18572 ];
+  networking.firewall.allowedTCPPorts = [ config.services.spotifyd.settings.zeroconf_port ];
 }