The default PHP version of Serv00 is 8.1, but Flarum 2.0 will stop supporting PHP 8.1.
Although the PHP version is changed to 8.3 using add-type, it still shows 8.1 when entering php flarum info or composer command via ssh.
This forum also uses Flarum, so if you don't upgrade the default PHP version, you may not be able to upgrade to the upcoming Flarum 2.0.