How can I add icon into ngx-bootstrap accordion-group heading?

You can set font awesome icon with below way.

<accordion-group [isOpen]="false" #accGroup>
  <button class="btn btn-light float-right">
    <i class="fa" [ngClass]="{'fa-arrow-down': accGroup?.isOpen, 'fa-arrow-up': !accGroup?.isOpen}"></i>
  </button>
</accordion-group>

I think it can be done like this..

<accordion-group #group>
    <span accordion-heading>
      <i class='fa fa-users'></i> Users
    </span>
    This content is straight in the template. 
</accordion-group>