Replace the empty author name with the source.

feedzy-replace-empty-author-name-with-source.php

<?php
/*
Plugin Name: Feedzy tweak - Replace the empty author name with the source
Version: 0.0.1
Author URI: https://themeisle.com
*/
add_filter( 'feedzy_meta_date', function( $date, $date_time, $feed_url, $item ) {
	$author      = $item->get_author();
	$permalink = $item->get_feed()->get_permalink();
	if ( empty($author) ) {
		$data .= __( $permalink, 'feedzy-rss-feeds' );
	}
	return $data;
}, 10, 4 );