Try fixing signald

nixos/roles/matrix-signal/mautrix-signal-module.nix

@@ -188,10 +188,9 @@ in
 
       restartTriggers = [ settingsFileUnsubstituted ];
     };
-    users.groups.mautrix-signal = { };
     users.users.mautrix-signal = {
       description = "Service user for the Matrix-Signal bridge";
-      group = "mautrix-signal";
+      group = "signald";
       isSystemUser = true;
     };
   };

nixos/roles/matrix-signal/signald-module.nix

@@ -26,7 +26,7 @@ in
 
 
   config = mkIf cfg.enable {
-    users.users."signald" = { isSystemUser = true; };
+    users.users."signald" = { isSystemUser = true; group = "signald"; };
     users.groups."signald" = { };
     systemd.tmpfiles.rules = [ "Z /var/lib/signald 0770 signald signald - -" ];
 
@@ -49,7 +49,6 @@ in
         ProtectControlGroups = true;
 
         DynamicUser = false;
-        PrivateTmp = true;
         Group = "signald";
         User = "signald";
         StateDirectory = "signald";
@@ -62,9 +61,6 @@ in
             --database=jdbc:sqlite:''${STATE_DIRECTORY}/signald.db
         '';
       };
-      unitConfig = {
-        JoinsNamespaceOf = "mautrix-signal.service";
-      };
     };
   };
 

overlays/10-previews.nix

@@ -7,4 +7,6 @@ in
   inherit (unstable) cachix nix-output-monitor cabal2nix;
   unstableHaskellPackages = unstable.haskellPackages;
   unstableGhc = unstable.ghc;
+  mautrix-signal = unstable.mautrix-signal;
+  signald = unstable.signald;
 }