On Bootstrap 3 this was pretty easy, you just had to change span and add whatever icon you wanted instead. But that doesn\'t seem the case with Bootstrap 4. Or maybe I\'m missin
A solution that allows to keep the HTML as it is and simply adding one CSS rule:
.dropdown-toggle::after {
border: none;
font: normal normal normal 12px/1 'Font Awesome 5 Free';
content: "\f078";
vertical-align: 0;
}
This will work with Font Awesome 5. The content property can be set to any available Unicode values. For example for the chevron-down (https://fontawesome.com/icons/chevron-down?style=solid) it's f078.