Hi there,
you can use this Filter hook:
https://docs.generatepress.com/article/generate_site_title_output/
This will output the default HTML with a FA star icon either side of the title text:
add_filter( 'generate_site_title_output', function( $output ) {
return sprintf(
'<%1$s class="main-title" itemprop="headline">
<a href="%2$s" rel="home">
<i class="fas fa-star"></i> %3$s <i class="fas fa-star"></i>
</a>
</%1$s>',
( is_front_page() && is_home() ) ? 'h1' : 'p',
esc_url( apply_filters( 'generate_site_title_href', home_url( '/' ) ) ),
get_bloginfo( 'name' )
);
});