Prefer GD over Imagick when choosing the default image editor.

prefer-gd.php

<?php
/**
 * Prefer GD over Imagick.
 *
 * @wordpress-plugin
 * Plugin Name: Prefer GD over Imagick.
 * Description: Switches the default image editor choice order.
 * Plugin URI:  
 * Version:     1.0.0
 * Author:      Adam Silverstein, Google
 * License:     Apache License 2.0
 * License URI: https://www.apache.org/licenses/LICENSE-2.0
 */

add_filter(
	'wp_image_editors', 
	function() {
		return array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
	}
);

Okay, very well! Thanks so much for the follow-up.

Do I need to hook into anything at all, or should I expect everything to "just work" merely by patching core in this way?

(I know that patching/hacking core is just for trying stuff as opposed to calling it a durable fix :D )

this should now be fixed in wp core