I have tried importing config files with ipv6 preferred over ipv4 (the advanced option to the right in the config generator), but apparently the NetworkManager "VPN plugin" fails to parse the line with either:
proto udp6
or
proto tcp6
An error message pops up and the file is not imported.
The ovpn configs can only be parsed with proto udp or proto tcp. Clearly the "VPN plugin" for NetworkManager (networkmanager-openvpn 1.8.10) is not working well and only allows ipv4.
Anyway, this is not a problem on AirVPN's side, but I hope this helps somebody else with this issue, and hopefully NetworkManager will get an update regarding this.
This issue is tracked there: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/issues/130 https://gitlab.gnome.org/GNOME/NetworkManager-openvpn/issues/18