<font-awesome-icon icon="fa-duotone fa-1" />
<FontAwesomeIcon icon="fa-duotone fa-1" />
.my-icon {
position: relative;
font: var(--fa-font-duotone);
font-style: normal;
}
.my-icon:before {
position: absolute;
content: "\31";
opacity:0.5
}
.my-icon:after {
content: "\31\31";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" style="width: 30px;height: 30px;fill: black">
<path d="M256 448c0 17.67-14.33 32-32 32H32c-17.67 0-32-14.33-32-32s14.33-32 32-32h64V123.8L49.75 154.6C35.02 164.5 15.19 160.4 5.375 145.8C-4.422 131.1-.4531 111.2 14.25 101.4l96-64c9.828-6.547 22.45-7.187 32.84-1.594C153.5 41.37 160 52.22 160 64.01v352h64C241.7 416 256 430.3 256 448z"/>
<path style="opacity: 0.5" d=""/>
</svg>
<i class="fa-duotone fa-1"></i>