Fix broken 4.1 update

fix.php

<?php
define('JOOMLA_MINIMUM_PHP', '7.2.5');

if (version_compare(PHP_VERSION, JOOMLA_MINIMUM_PHP, '<')) {
	die(str_replace(
			'{{phpversion}}',
			JOOMLA_MINIMUM_PHP,
			file_get_contents(dirname(__FILE__) . '/templates/system/incompatible.html')
		));
}

// Constant that is checked in included files to prevent direct access.
define('_JEXEC', 1);
define('JPATH_BASE', __DIR__);

if (file_exists(__DIR__ . '/includes/defines.php')) {
	require_once __DIR__ . '/includes/defines.php';
}
if (!defined('_JDEFINES')) {
	require_once JPATH_BASE . '/includes/defines.php';
}

// Check for presence of vendor dependencies not included in the git repository
if (!file_exists(JPATH_LIBRARIES . '/vendor/autoload.php') || !is_dir(JPATH_ROOT . '/media/vendor')) {
	echo file_get_contents(JPATH_ROOT . '/templates/system/build_incomplete.html');
	exit;
}

// Add the JLoader, etc...
require_once JPATH_BASE . '/includes/framework.php';

// Boot the DI container
$container = \Joomla\CMS\Factory::getContainer();
$db        = \Joomla\CMS\Factory::getContainer()->get('DatabaseDriver');
$msg       = [];

foreach(['atum', 'cassiopeia'] as $template) {
	$clientId = $template === 'atum' ? 1 : 0;
	$query = $db->getQuery(true)
		->update($db->quoteName('#__template_styles'))
		->set($db->quoteName('inheritable') . ' = 1')
		->where($db->quoteName('template') . ' = ' . $db->quote($template))
		->where($db->quoteName('client_id') . ' = ' . $clientId);

	try {
		$db->setQuery($query)->execute();
	} catch (Exception $e) {
		$msg[] = \Joomla\CMS\Language\Text::sprintf('JLIB_DATABASE_ERROR_FUNCTION_FAILED', $e->getCode(), $e->getMessage()) . '<br>';
	}
}

echo implode('<br>', count($msg) ? $msg : ['Successfully updated the template styles']);
die;

instructions.md

• Upload the file fix.php in your server at the root folder (where the .htaccess and the index.php are)
• Temporarily rename .htaccess to .htaccess.bak (needed only for sites with AdminTools)
• Visit your site's /fix.php (eg https://mydonain.tld/fix.php)
• Delete the fix.php file
• Restore .htaccess.bak to .htaccess (needed only for sites with AdminTools)

be aware that if you are using an htaccess file created by admintools or similar then you will need to disable it before you will be able to run fix.php. and dont forget to turn it back on afterwards

I've updated the instructions, thanks Brian!

This is not fixing my problem - both templates are still gone!

This is not fixing my problem - both templates are still gone!

Then you have another problem, probably your update was unsuccessful and you're missing files.

Hmm.. but the update went through without errors.. How do I reinstall core files in joomla 4.1 ? Is that not possible anymore like in 3.x ?

And the problem only arose after doing the database repair !? It worked before the repair.

Top, thx! 👍🏼