Ubuntu 22.04 supports PHP 8.1 by default. However, Moodle is not compatible with PHP 8.1, so release 7.4 must be used instead. If PHP 8.1 is already installed on the Linode, you must install PHP 7.4 and configure it as the active release of PHP. PHP 7.3 is also supported, but 7.4 is highly recommended. See the Moodle and PHP page for compatibility information.