[Mashiro]

There are some requirements for IPv6 over IPv4 to make it work of which some important are:
- a dedicated WAN IPv4 IP address that is not a CGNAT IP address
- ICMP communication must be possible to your public WAN IPv4 IP address from outside
- if behind a NAT the NAT must support and have IP routing and forwarding enabled
- a possible firewall shouldn't block the tunnel endpoints

As said before the interface you see is not for IPv6 over IPv4 configuration and I haven't found a single word for IPv6 over IPv4 for that router you have. There are some more expensive routers from Huawei that are probably business/enterprise that allow IPv6 over IPv4 via command line / terminal configuration.

While I have native IPv6 now I have never been able to use IPv6 over IPv4 at home because the setup of my ISP simply didn't meet the requirements.