BT Home Hub 5 behind a BT Smart Hub and OpenVPN

I have a BT Home Hub 5, flashed with LEDE sitting behind a Bt Smart Hub. Everything is working fine between the routers. However, I am trying to get OpenVPN on the Home Hub 5 to connect though the Smart Hub to a VPN provider. Can anyone please point me in the right direction?

For any novices who may be interested, I've written a tutorial to show how to install and configure OpenVPN client on HH5a to work with a free VPN service provider.

It does make use of WinSCP, so will require a Microsoft Windows computer.

PDF can be downloaded from here:
https://openwrt.ebilan.co.uk/viewtopic.php?f=7&t=279

@rgb69 Do you have Smart Hub Type A or Type B? I'm trying to get info about Type B to see if it can be supported.

There is presently no OpenWRT support at present for the Smart Hub type B
link to ebilan forum

Thanks. I was actually looking for more technical info to see if it can be supported. But the photos don't show the chipsets numbers.