<font-awesome-icon icon="fa-brands fa-buysellads" />
<FontAwesomeIcon icon="fa-brands fa-buysellads" />
.my-icon::before {
font: var(--fa-font-brands);
content: "\f20d";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512" style="width: 30px;height: 30px;fill: black">
<path d="M224 150.7l42.9 160.7h-85.8L224 150.7zM448 80v352c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V80c0-26.5 21.5-48 48-48h352c26.5 0 48 21.5 48 48zm-65.3 325.3l-94.5-298.7H159.8L65.3 405.3H156l111.7-91.6 24.2 91.6h90.8z"/>
</svg>
<i class="fa-brands fa-buysellads"></i>