bootstrap-4-4-4.html.twig in Bootstrap Layouts 8

<div class="row">
    {% 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 %}
</div>