if you wishes to remove the link from the public portal.
Concerning the link from the HTML Template, we do see that once we remove the Powered_by macros a new tag <center> appears with this content
<a id="powered_by_text" href="https://www.beyondtrust.com/remote-support" class="inverse" target="_blank" rel="noopener">BeyondTrust Remote Support</a>
This is by design and cannot be removed. It would be best to submit this as a Feature Request.