create bootstrap columns inside editor group block

Inside your .row container choose a “Columns Block” instead of a paragraph block. Each column can be assigned the desired bootstrap CSS class. It will look like this:

<div class="wp-block-group container">
   <div class="wp-block-group__inner-container">
      <div class="wp-block-group row">
         <div class="wp-block-group__inner-container">
            <div class="wp-block-columns">
               <div class="wp-block-column col-sm-12 col-md-6 col-lg-6">
                  <p>Text Here</p>
               </div>
               <div class="wp-block-column col-sm-12 col-md-6 col-lg-6">
                  <p>More Text</p>
               </div>
            </div>
         </div>
      </div>
   </div>
</div>

The “Columns Block” is already a flex container by default, so in this case you may not even need the .row container. Or you could give the .row class to the “Columns Block” itself.