I bought the InvizBox GO mobile privacy router that uses OpenWRT firmware based on LEDE, great product.
The device comes with 2 months of premium VPN included (IPVanish). I already have a lifetime account on another provider, and I like to add this config to the router but I don't know how.
In the admin UI I can select a VPN location (IPVanish) from a predefined list, maybe I could I add my VPN config to this list as a custom entry.
The FAQ states: Can I use my own VPN service with the InvizBox Go?
Unfortunately, at the moment, the short answer is no as we've built our services around one specific VPN partner.
The slightly longer answer is that our product is a linux router (OpenWRT based) which is configured to use OpenVPN in a specific way. If you're knowledgeable enough in Linux and networking, you should be able to change the configurations to work with your own VPN. But we're not going to be able to provide you with instructions or support for this.
If you go for option two, have fun. The InvizBox Go is a nice piece of hardware to hack (if you go too far, we're here)!
It depends on how much did they modify OpenWRT to adapt it to their needs; apparently, you can have a look at the source code at https://github.com/invizbox/invizbox. My guess is that they only modified the web interface, so you can just edit the configuration files by hand. Or you could try to build a new firmware for it, using the OpenWRT / LEDE sources and their configuration files, and have a fully functional device.