For me, it worked, but it wasn’t .discourse-tag.bullet::before but this:
@import url("https://use.fontawesome.com/releases/v5.13.0/css/all.css");
.discourse-tag.box::before {
top: 0em;
margin-right: 5px;
content: "\f02b";
color: #bbbdbb;
background: none;
height: 16px; /* You might need to fix this a little for mobile view */
font-weight: 900;
font-size: 0.9em;
font-family: "Font Awesome 5 Free"; /* This is the correct font-family*/
}
.extra-info-wrapper .discourse-tag.box {
background:none;
}
.discourse-tag.box {
background:none;
}