Surely for it to be a 'secure VPN server' there has got to be some stuff set up first, like setting up key only login, disabling root ssh login, disabling everything ssh, setting up firewall, disabling ipv6 entirely in the case of openvpn?
I run a vpn on digital ocean and its amazing looking at the logs and seeing how quickly, and how many attempts there are to break into the server straight after setting it up. As a person who isnt completely sure of what i am doing when it comes to firewalls and setting up 'jails' or whatever, this kinda makes me uneasy. I wouldnt even be sure how to tell if anyone had broken in to my server...
https://www.linode.com/docs/networking/vpn/set-up-a-hardened...
This has been the most useful guide that I have found on setting up an openvpn server. It has a bunch of steps to go through before you get to actually installing openvpn. But as I said, I am not that knowledgeable myself when it comes to running a server, so this may all just be unnecessary.