update_db_utf8mb4.php

<?php

function update_db_to_utf8mb4() {
	if (!isset($_GET['update-utf8bm4'])) {
		return;
	}
  
	require_once( ABSPATH . 'wp-admin/includes/upgrade.php');

	/** WordPress Administration API */
	require_once(ABSPATH . 'wp-admin/includes/admin.php');

	/** WordPress Schema API */
	require_once(ABSPATH . 'wp-admin/includes/schema.php');

	$tables = $wpdb->tables('all');
	if (!wp_should_upgrade_global_tables()) {
		$global_tables = $wpdb->tables('global');
		$tables = array_diff_assoc($tables, $global_tables);
	}

	foreach ($tables as $table) {
		maybe_convert_table_to_utf8mb4($table);
	}
}
add_action('wp_loaded', 'update_db_to_utf8mb4');

Is it intended that in !isset($_GET['update-utf8bm4']) it is update-utf8bm4 and not update-utf8mb4?
Anyone using this script should pay attention to that.

Would be handy to update this to account for multisite too.