diff --git a/nixops/desktop.nix b/nixops/desktop.nix
index f4455fd..1c417f3 100644
--- a/nixops/desktop.nix
+++ b/nixops/desktop.nix
@@ -3,12 +3,6 @@
 { config, pkgs, ... }:
 let
   m-labs = import (fetchTarball https://nixbld.m-labs.hk/channel/custom/artiq/full/artiq-full/nixexprs.tar.xz) { inherit pkgs; };
-  pkgs-unstable = import (pkgs.fetchFromGitHub {
-    owner = "nixos";
-    repo = "nixpkgs";
-    rev = "2ec0c698eaf3e7a4d13988538f08d65b3d006f40";
-    sha256 = "137py5fhmjs3p1dgqmd7cxsxzzs67nrqqijxmflb0ck1fnfzrij7";
-  }) {};
 in
 {
   deployment.targetHost = host;
@@ -46,10 +40,12 @@ in
     gimp imagemagick
     (python3.withPackages(ps: with ps; [ numpy scipy matplotlib qtconsole regex ]))
     mosh psmisc libreoffice-fresh
-    gtkwave telnet unzip zip gnupg
+    gtkwave unzip zip gnupg
     gnome3.gnome-tweaks
     jq sublime3 rink qemu_kvm
-    tmux xc3sprog m-labs.openocd screen gdb minicom picocom tigervnc
+    tmux screen gdb minicom picocom tigervnc
+    # TODO m-labs.openocd
+    # TODO xc3sprog
     emacs bat ripgrep
     xpra
     rust-analyzer
@@ -58,7 +54,7 @@ in
         vscode-extensions.matklad.rust-analyzer
       ];
     })
-    pkgs-unstable.joplin-desktop
+    joplin-desktop
     virt-manager spice-gtk
     any-nix-shell
   ];
@@ -115,7 +111,6 @@ in
   sound.enable = true;
   hardware.pulseaudio = {
     enable = true;
-    extraModules = [ pkgs.pulseaudio-modules-bt ];
     package = pkgs.pulseaudioFull;
   };
 
@@ -157,15 +152,14 @@ in
   users.extraGroups.plugdev = { };
   users.extraUsers = import ./common-users.nix { inherit pkgs; };
   security.sudo.wheelNeedsPassword = false;
-  services.udev.packages = [ m-labs.openocd ];
+  # TODO services.udev.packages = [ m-labs.openocd ];
   services.udev.extraRules = (import ./extra-udev.nix);
 
   nix.binaryCachePublicKeys = ["nixbld.m-labs.hk-1:5aSRVA5b320xbNvu30tqxVPXpld73bhtOeH6uAjRyHc="];
   nix.binaryCaches = ["https://nixbld.m-labs.hk" "https://cache.nixos.org"];
   nix.sandboxPaths = ["/opt"];
 
-  nix.package = pkgs.nix_2_4;
   nix.extraOptions = ''
-    experimental-features = nix-command flakes
+    experimental-features = nix-command flakes ca-derivations impure-derivations
   '';
 }
diff --git a/nixops/light.nix b/nixops/light.nix
index d55afd0..8861110 100644
--- a/nixops/light.nix
+++ b/nixops/light.nix
@@ -39,7 +39,7 @@ in
     evince
     (python3.withPackages(ps: with ps; [ numpy scipy ]))
     psmisc
-    telnet unzip zip gnupg
+    unzip zip gnupg
     sublime3 rink
     tmux screen tigervnc
     any-nix-shell
@@ -87,7 +87,6 @@ in
   sound.enable = true;
   hardware.pulseaudio = {
     enable = true;
-    extraModules = [ pkgs.pulseaudio-modules-bt ];
     package = pkgs.pulseaudioFull;
   };
 
@@ -127,15 +126,14 @@ in
   users.extraUsers = import ./common-users.nix { inherit pkgs; };
   
   security.sudo.wheelNeedsPassword = false;
-  services.udev.packages = [ m-labs.openocd ];
+  # TODO services.udev.packages = [ m-labs.openocd ];
   services.udev.extraRules = (import ./extra-udev.nix);
 
   nix.binaryCachePublicKeys = ["nixbld.m-labs.hk-1:5aSRVA5b320xbNvu30tqxVPXpld73bhtOeH6uAjRyHc="];
   nix.binaryCaches = ["https://nixbld.m-labs.hk" "https://cache.nixos.org"];
   nix.sandboxPaths = ["/opt"];
 
-  nix.package = pkgs.nix_2_4;
   nix.extraOptions = ''
-    experimental-features = nix-command flakes
+    experimental-features = nix-command flakes ca-derivations impure-derivations
   '';
 }
diff --git a/nixops/rpi-server.nix b/nixops/rpi-server.nix
index d02c663..5c37758 100644
--- a/nixops/rpi-server.nix
+++ b/nixops/rpi-server.nix
@@ -10,10 +10,6 @@
 
   boot.loader.grub.enable = false;
   boot.loader.generic-extlinux-compatible.enable = true;
-  boot.loader.raspberryPi = pkgs.lib.mkIf rpi4 {
-    enable = true;
-    version = 4;
-  };
   boot.kernelParams = ["cma=64M"]; # work around https://github.com/raspberrypi/linux/issues/3208
   boot.kernelPackages = if rpi4 then pkgs.linuxPackages_rpi4 else pkgs.linuxPackages_rpi3;
   boot.initrd.includeDefaultModules = false;
@@ -119,7 +115,7 @@
 
   documentation.enable = false;
   environment.systemPackages = with pkgs; [
-    psmisc wget vim git sshfs usbutils lm_sensors file telnet mosh tmux
+    psmisc wget vim git sshfs usbutils lm_sensors file mosh tmux
     imagemagick
   ];
   programs.fish.enable = true;
@@ -146,8 +142,7 @@
   nix.binaryCaches = ["https://cache.nixos.org" "https://nixbld.m-labs.hk"];
   nix.trustedUsers = ["root" "nix"];
 
-  nix.package = pkgs.nix_2_4;
   nix.extraOptions = ''
-    experimental-features = nix-command flakes
+    experimental-features = nix-command flakes ca-derivations impure-derivations
   '';
 }
diff --git a/nixops/rpi.nix b/nixops/rpi.nix
index 5aca52b..eef2a9f 100644
--- a/nixops/rpi.nix
+++ b/nixops/rpi.nix
@@ -72,7 +72,8 @@ in
 
   documentation.enable = false;
   environment.systemPackages = with pkgs; [
-    psmisc wget vim git sshfs usbutils uhubctl lm_sensors file telnet mosh tmux xc3sprog m-labs.openocd screen gdb minicom picocom
+    psmisc wget vim git sshfs usbutils uhubctl lm_sensors file mosh tmux m-labs.openocd screen gdb minicom picocom
+    # TODO xc3sprog
   ];
   programs.fish.enable = true;
   programs.wireshark.enable = true;
@@ -81,8 +82,7 @@ in
   nix.binaryCaches = ["https://cache.nixos.org" "https://nixbld.m-labs.hk"];
   nix.trustedUsers = ["root" "nix" "sb"];
 
-  nix.package = pkgs.nix_2_4;
   nix.extraOptions = ''
-    experimental-features = nix-command flakes
+    experimental-features = nix-command flakes ca-derivations impure-derivations
   '';
 }