use submission completed_at

app/controllers/submissions_dashboard_controller.rb

@@ -13,11 +13,12 @@ class SubmissionsDashboardController < ApplicationController
     @submissions = Submissions.search(current_user, @submissions, params[:q], search_template: true)
     @submissions = Submissions::Filter.call(@submissions, current_user, params)
 
-    @submissions = if params[:completed_at_from].present? || params[:completed_at_to].present?
-                     @submissions.order(Submitter.arel_table[:completed_at].maximum.desc)
-                   else
-                     @submissions.order(id: :desc)
-                   end
+    @submissions =
+      if params[:status] == 'completed' || params[:completed_at_from].present? || params[:completed_at_to].present?
+        @submissions.order(completed_at: :desc)
+      else
+        @submissions.order(id: :desc)
+      end
 
     @pagy, @submissions = pagy_auto(@submissions.select_for_list.preload(submitters: :start_form_submission_events))