<font-awesome-icon icon="fa-light fa-1" />
<FontAwesomeIcon icon="fa-light fa-1" />
.my-icon::before {
font: var(--fa-font-light);
content: "\31";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" style="width: 30px;height: 30px;fill: black">
<path d="M256 464c0 8.844-7.156 16-16 16h-224C7.156 480 0 472.8 0 464S7.156 448 16 448h96V78.72L57.17 117.1C49.95 122.2 39.95 120.4 34.89 113.2C29.83 105.9 31.58 95.97 38.83 90.91l80-55.1c4.891-3.438 11.28-3.875 16.56-1.094C140.7 36.57 144 42.04 144 48.01V448h96C248.8 448 256 455.2 256 464z"/>
</svg>
<i class="fa-light fa-1"></i>