I am based in the UK and my ISP is EE.
The modem/router of the ISP is the primary one while my GL.iNet Flint 2 GL-MT6000 router (firmware 4.6.8 release1) is the secondary one: the physical connection goes from the WAN port of the Flint 2 router to a LAN port of the primary modem/router of the ISP.
On the Flint 2 I have set an OpenVPN Client connected to my NordVPN account so that the WiFi irradiated by the Flint 2 is the NordVPN one (the OpenVPN Client on the Flint 2 connects to NordVPN servers in Italy or in UK).
When my Android phone connects to the OpenVPN Client WiFi from the Flint 2, everything is working fine in terms of VPN and I have no need to install the NordVPN app on my phone (which is what I want).
The only exception at the moment is that when my phone is connected to the OpenVPN Client WiFi from the Flint 2, I am not able to have WiFi calls.
Is there a way to have WiFi calls when my phone is connected to that OpenVPN Client WiFi from the Flint 2?
Should the WiFi calls be routed outside the VPN while everything else (browsing, apps, etc) remain inside the VPN?
I would imagine that the Proxy mode settings in the VPN Dashboard might be one place where to work on the Flint 2 settings, but I am not quite sure of what could be done and how.
Please note: I am not an expert at all and it is quite likely I'll initially get lost in technical answers.
WiFi calling is generally limited to the same region of your carrier.
As you are in the UK and you have to use an UK IP address so that you WiFi calling work. If you go to other countries e.g. US and want to enjoy the WiFi calling from UK, that is generally not possible. The carrier need to charge you money and will not let you roam.
So the problem is that, when you use Nord, your IP goes to another country and WiFi calling stopped to work.
To solve this, use an Nord server from the UK and try again.
As I mentioned in my initial text "the OpenVPN Client on the Flint 2 connects to NordVPN servers in Italy or in UK" this means that WiFi calls are not working with a UK IP nor with an Italian IP.
Any suggestions on how I could have WiFi calls when my phone is connected to the OpenVPN Client WiFi from the Flint 2?
If your carrier is UK and when you go to Italy with your phone and the phone roam to Italy carrier network, your carrier will disable WiFi callling already.
This is because your carrier intentially to do so.
In this case vpn does not matter then.
My mobile carrier is Vodafone UK and my issue is from UK exclusively.
UK is where I use the Flint 2 with the OpenVPN Client account connected to my NordVPN account.
WiFi calls are not working when from the UK I connect my Android phone to the Flint 2 VPN WiFi (either through a UK NordVPN server or through an Italian NordVPN server).
WiFi calls are working OK when from the UK I connect my Android phone to the EE WiFi (EE is my UK ISP and the EE WiFi comes from my primary modem/router, like initially detailed in this thread).