Some ISPs in Japan use a convoluted solution to deliver IPv4 over IPv6 called V6Plus. I have the RT-AX56U which has an option for V6 but when this is selected you get a MAP-E port mismatch error or a Map server did not reply response. So I'm stuck on the much slower PPPoE connection. Is there some way to fix or patch this? Because it sounds like this can be fixed/patched. Im not sure if ASUS care as the last firmware update was in the middle of last year.