This was in your initial commit already:
2584dc1#diff-ad9fb94d48b0a156f12a7c3972ef9db886e2eb46f6626bafb146cd53d7d77c69R119

Who knows which feature accidentally work due to this class being existent right now.
Changing would be quite a BC break.

Anyway, a dashboard with same height widgets works perfectly fine for me with that HTML:

You can simply add a second div with the wanted CSS classes and everything works fine.

This was in your initial commit already

Yes, I was looking for when/why we do that, it was there from the beginning:
657ea71#diff-77f98db4bbf74ae14cad716cd52d662106d4ea5a78039716a76307c9745b7be9R112-R114

Who knows which feature accidentally work due to this class being existent right now.
Changing would be quite a BC break.

Yes, it could, testing in the table preview, there is no big impact:

1. The .content class does nothing
2. .row .row-cards add the same margin as .page-body.

• The only impact is if you have a js/css selector targeting this.
• Starting a page directly with some .col without .row (because we add it in the base template)

Do you want to sent a PR with the changes?
I will try then apply your changes locally and test for a while to see if anything weird happens.

Do you want to sent a PR with the changes?

Yes I can
Do we keep the section.content element?

I though you only replace <div class="row row-cards"> with <div class="row">.

This PR change will definitely blow up my app. I use both blocks / the section as selector in JS and CSS:

{% block page_content_class %}{{ parent() }} {% block page_class %}{% endblock %}{% endblock %}

And I am almost certain I will find more references if I search more detailed:

I though you only replace <div class="row row-cards"> with <div class="row">.

No 😢

This PR change will definitely blow up my app

We have a project where another developer also uses/overrides these blocks.
The quick fix was to update the base.html.twig with:

{% block page_content_before %}
   <div class="row row-cards">
      <section id="{% block page_content_id %}{% endblock %}" class="{% block page_content_class %}content{% endblock %}">
{% endblock %}

{% block page_content_after %}
      </section>
   </div>
{% endblock %}

It is a temporary patch to avoid the BC break but will/should not be left that way.

The end goal it that every pages that uses {% block page_content %}{% endblock %} should look like this now:

{% block page_content %}
    <div class="row row-cards">
        <div class="col-sm-6 col-lg-3"></div>
        <div class="col-sm-6 col-lg-3"></div>
        <div class="col-sm-6 col-lg-3"></div>
        <div class="col-sm-6 col-lg-3"></div>
    </div>
{% endblock %}

{% block page_content %}
    <div class="col-sm-6 col-lg-3"></div>
    <div class="col-sm-6 col-lg-3"></div>
    <div class="col-sm-6 col-lg-3"></div>
    <div class="col-sm-6 col-lg-3"></div>
{% endblock %}

OR

{% block page_content %}
    <div class="row justify-content-center">
    	<div class="col-8">
             <div class="card"></div>
    	</div>
    </div>
{% endblock %}

{% block page_content %}
    <div class="justify-content-center">
    	<div class="col-8">
             <div class="card"></div>
    	</div>
    </div>
{% endblock %}