You can use Algo to configure a pre-existing server as an AlgoVPN rather than using it to create and configure a new server on a supported cloud provider. This is referred to as a local installation rather than a cloud deployment.
Install the Algo scripts following the normal installation instructions, then choose:
Install to existing Ubuntu 18.04, 19.04, or 19.10 server (Advanced)
Make sure your target server is running an unmodified copy of the operating system version specified. The target can be the same system where you've installed the Algo scripts, or a remote system that you are able to access as root via SSH without needing to enter the SSH key passphrase (such as when using ssh-agent).
PLEASE NOTE: Algo is intended for use to create a dedicated VPN server. No uninstallation option is provided. If you install Algo on an existing server any existing services might break. In particular, the firewall rules will be overwritten. See AlgoVPN and Firewalls for more information.