zammad/app/views/knowledge_base/public/not_found.html.erb

<main class="main main--error">
  <div class="container">
    <%= icon('mood-sad') %>
    <h1><%= zt('Page not found') %></h1>
    <p>
      <%= zt('The page you were looking for does not exist.') %>
      <%= link_to zt('Click here'), custom_path_if_needed(help_root_path(locale: fallback_locale.locale), @knowledge_base) %>
      <%= zt('to go to the homepage.') %>
    </p>
  </div>
</main>