The iThemes Security Extension throws the following critical error with PHP 8:
An error of type E_ERROR was caused in line 499 of the file /www/htdocs/w01af748/xxx/wp-content/plugins/mainwp-ithemes-security-extension/core/admin-pages/page-settings.php. Error message: Uncaught TypeError: implode(): Argument #2 ($array) must be of type ?array, string given in /www/htdocs/w01af748/xxx/wp-content/plugins/mainwp-ithemes-security-extension/core/admin-pages/page-settings.php:499