Hi @yingfuli,
Thanks for reaching out.
You could use HTML icon instead of shortcode icon, example,
<i class="x-icon" data-x-icon-s=""></i>
Where the icon code f641
( 
) is from https://fontawesome.com/icons?d=gallery.
There are 3 attributes depending on icon,
data-x-icon-s data-x-icon-b data-x-icon-o
It’s for solid icons (like https://fontawesome.com/icons/ad?style=solid ), then for brand icons (like https://fontawesome.com/icons/500px?style=brands), and then for outline and regular icons (like https://fontawesome.com/icons/angry?style=regular).
BUT, not all icons are achievable, especially the new ones that aren’t still integrated to the theme.
Thanks!