Although I’m not running XFCE at the moment, IIRC Network Manager runs nearly the same on every Desktop.
After opening Network Manager, you should see a VPN tab. Click on that, and create a new VPN configuration, selecting OpenVPN as the VPN technology, specifying the certificate to be used, the VPN service URL and providing your credentials. After that, you should have a connection which can be invoked at any time by clicking on it.
Although it’s unlikely that any VPN provider would implement OpenVPN is some non-standard way, does your VPN provider provide documentation how they recommend connecting?
Although creating a Network Manager VPN connection should be fairly straightforward, am curious where you may have gotten libvpn and exactly how you think you may be using it… AFAIK it’s not part of the main openSUSE repos in any way (even source). is this something provided by your VPN provider?
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