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<div class="d-block d-md-none"> This will show only in BELOW MEDIUM form factors</div>
<div class="d-none d-md-block">This will show in MEDIUM AND UP</div>

also possible to include direcly in the <> tag:
<br class="d-block d-xl-none"/>
<br class="d-block d-xl-none"/>
source:
https://stackoverflow.com/questions/14207109/hiding-elements-in-responsive-layout