PHP 8 is now available in the LAMP app
To use PHP 8, install the LAMP app and switch the PHP version to 8.0 . See https://docs.cloudron.io/apps/lamp/#supported-php-versions for more information.
You can also do the above for your existing PHP 7.4 app. In the future, as new PHP versions are added, this will make it easier to switch PHP version in your app.