The "margin-bottom" property of the breadcrumb is fixed in "1rem"
I usually use the breadcrumb without margin-bottom, or margin-bottom: 0. I think it would be interesting to define a variable for this property ...
Something like:
$breadcrumb-margin: 0 0 1rem! Default;

.breadcrumb {
   ...
   margin: $breadcrumb-margin;
   {Instead of margin-bottom}
   ...
}

*Note: We could even remove the property, since we can define the margins with the classes "m- , mb - * ..."