add_filter(
   'friends_no_comments_feed_available',
    function(
        string $no_comments_yet_,
        $post_id,
        $friend_user,
        $user_feed
    ) {
        // Your code here.
        return $no_comments_yet_;
    },
    10,
    4
);

apply_filters( 'friends_no_comments_feed_available', __( 'No comments yet.', 'friends' ), $post_id, $friend_user, $user_feed )