default-archive-card-img.php

<?php
function default_archive_card_img($args){
	if(empty($args["featured_image"]))
		$args["featured_image"] = blocksy_media(array(
			"attachment_id"=>get_page_by_path("default_image_name")->ID,
			'ratio' => '4/3',
			'class' => 'boundless-image',
			'tag_name' => 'a',
			'size' => "medium_large",
			'html_atts' => [
				'href' => esc_url(get_permalink()),
				'aria-label' => wp_strip_all_tags(get_the_title()),
			]
		));
	return $args;
}
add_filter('blocksy:archive:render-card-layers','default_archive_card_img');