bootstrap-4-4-4-stacked.html.twig in Bootstrap Layouts 8.3

<div {{ attributes.addClass('row') }} >
  {{ title_suffix.contextual_links }}
  {% if content.top %}
  <div class="col-sm-12">
    {{ content.top }}
  </div>
  {% endif %}

  {% if content.sidebar_left %}
  <div class="col-sm-4">
    {{ content.sidebar_left }}
  </div>
  {% endif %}
  {% if content.main %}
  <div class="col-sm-4">
    {{ content.main }}
  </div>
  {% endif %}

  {% if content.sidebar_right %}
  <div class="col-sm-4">
    {{ content.sidebar_right }}
  </div>
  {% endif %}

  {% if content.bottom %}
  <div class="col-sm-12">
    {{ content.bottom }}
  </div>
  {% endif %}
</div>