Font Awesome 5 use social/brand icons in React

import { FontAwesomeIcon } from "@fortawesome/react-fontawesome"
import { faFacebook } from "@fortawesome/free-brands-svg-icons"

const icon = <FontAwesomeIcon icon={faFacebook} />

I found the spelling/casing of the brand icons on FontAwesome's GitHub

Try:

<FontAwesomeIcon icon={['fab', 'facebook-f']} />

Note that font awesome now has different icon sets. The solid set (fas) is the default. The facebook icon is in the brands set (fab).