I was not able to test it (for example borrowing a residential IP in a different country) but I suspect they detect OpenVPN via packets inspection, like this ex

I was not able to test it (for example borrowing a residential IP in a different country) but I suspect they detect OpenVPN via packets inspection, like this example: "Detecting VPN (and its configuration!) and proxy users on the server side" by @ValdikSS https://medium.com/@ValdikSS/detecting-vpn-and-its-configuration-and-proxy-users-on-the-server-side-1bcc59742413#.forbbpie6 https://medium.com/@ValdikSS/detecting-vpn-and-its-configura...