wordpress-change-registration-url.php

<?php

/**
 * Plugin Name:       Change registration url
 * Description:       You need to edit the plugin file in an editor for it to work! 
 * Author:            Florian Egermann
 * Author URI:        https://www.fleg.de/
 */


add_filter( 'register_url', 'custom_register_url' );

function custom_register_url( $register_url )
{
	$register_url = "https://my-domain.dev/register"; // replace with your registration page url
	return $register_url;
}
?>