finally vivaldi is fixed, had to delete the desktop item in .local/share/application and let it be repopuated

modules/nixos/apps/vivaldi/default.nix

@@ -19,6 +19,9 @@ in
     environment.systemPackages = with pkgs; [
       vivaldi
       vivaldi-ffmpeg-codecs
+      qt5.qtwayland
     ];
+
+    # environment.sessionVariables.NIXOS_OZONE_WL = "1";
   };
 }

modules/nixos/graphical-interface/desktop-manager/kde/default.nix

@@ -15,7 +15,10 @@ in
   };
 
   config = mkIf cfg.enable {
-    environment.systemPackages = with pkgs; [ xdg-utils ];
+    environment.systemPackages = with pkgs; [
+      xdg-utils
+      kdePackages.qtbase
+    ];
 
     services = {
       xserver = enabled;