The last time I tried OpenVPN the client seemed to primarily be a vehicle for displaying ads for a VPN service that I wasn't interested in (I wanted to VPN back to my home network, not to an endpoint in another country).
I don't know what you used, but the official OpenVPN apps are all ad free as far as I can tell.
This is "OpenVPN Connect" by "OpenVPN Technologies".
The app store listing currently shows that they removed the Private Tunnel section and made that into a separate app. The private tunnel is the advertising I was referring to.