GL.Inet gl-ax1800 router now Wifi calling on airplane mode wont work

As I know IPsec is completely insecure protocol. Microsoft developments is insecure by default (as my practice shown).

More info here

So I advise against using this. But… Calls is insecure by default both WiFi calls or SS7.

At the risk of going off topic, citing 10 - 15 year old security flaws that were patched is hardly proof of insecurity. To get back on topic.

What the OP and others are asking is there a way to get wifi calling working when using another VPN. Many wifi calling providers use IKEv2 protocol. I recommend they find the hostnames for the wifi calling endpoints. Then if there is a way to specify certain destinations to bypass their VPN. For example, att wifi calling:

EDIT: T-Mobile

and here