Please use this code
add_filter( 'fep_filter_user_name', function( $name, $id ){
if ( $name && function_exists( 'um_fetch_user' ) && fep_get_the_id() ) {
um_fetch_user( $id );
$name = '<a href="' . um_user_profile_url() . '">' . $name . '</a>';
}
return $name;
}, 10, 2);