Hello!
Many people have requested OpenVPN for Windows 10 Mobile so far.
One problem in the past the lack of a VPN API, which now exists and seems to work for all UWP apps.
A reference can be found here:
https://docs.microsoft.com/en-us/uwp/api/Windows.Networking.Vpn
I hope OpenVPN can eventually be brought to Windows UWP.
Regards,
Benedikt