Thank you so much, that got me on the right track!
Now it works ~
<script src="https://kit.fontawesome.com/{{YOUR_CODE}}.js" crossorigin="anonymous"></script>
<style>
:where(.nav, .gh-navigation-menu) .nav-bluesky a,
:where(.nav, .gh-navigation-menu) .nav-linkedin a,
:where(.nav, .gh-navigation-menu) .nav-keybase a,
:where(.nav, .gh-navigation-menu) .nav-rss a {
font-size: 0 !important;
}
:where(.nav, .gh-navigation-menu) .nav-bluesky a::before,
:where(.nav, .gh-navigation-menu) .nav-linkedin a::before,
:where(.nav, .gh-navigation-menu) .nav-keybase a::before,
:where(.nav, .gh-navigation-menu) .nav-rss a::before {
font-family: "Font Awesome Free";
display: inline-block;
font-size: 20px;
font-style: normal;
font-weight: normal;
font-variant: normal;
text-rendering: auto;
-webkit-font-smoothing: antialiased;
}
:where(.nav, .gh-navigation-menu) .nav-bluesky a::before {content: "\e6a3"}
:where(.nav, .gh-navigation-menu) .nav-linkedin a::before {content: "\f08c"}
:where(.nav, .gh-navigation-menu) .nav-keybase a::before {content: "\f4f5"}
:where(.nav, .gh-navigation-menu) .nav-rss a::before {content: "\f143"}
:where(.nav, .gh-footer-menu) .nav-bluesky a::before,
:where(.nav, .gh-footer-menu) .nav-linkedin a::before,
:where(.nav, .gh-footer-menu) .nav-keybase a::before,
:where(.nav, .gh-footer-menu) .nav-rss a::before {
font-family: "FontAwesome";
display: inline-block;
font-size: 20px;
font-style: normal;
font-weight: normal;
font-variant: normal;
text-rendering: auto;
-webkit-font-smoothing: antialiased;
}
:where(.nav, .gh-footer-menu) .nav-bluesky a::before {content: "\e6a3"}
:where(.nav, .gh-footer-menu) .nav-linkedin a::before {content: "\f08c"}
:where(.nav, .gh-footer-menu) .nav-keybase a::before {content: "\f4f5"}
:where(.nav, .gh-footer-menu) .nav-rss a::before {content: "\f143"}
</style>