My server is running on Virtuozzo container and I'd like to upgrade to CloudLinux. Is this something I can do?
No. CloudLinux has ended the support for Virtuozzo container. However, CloudLinux continues to offer support for Virtuozzo hypervisor and OpenVZ.
This means, you can use CloudLinux if you are running on hypervisor instead of container.
You can check your server environment by the following command:
cat /var/cpanel/envtype ; echo