Clients on Orbi Wi-Fi receive an IPv6 default gateway from an Orbi unit

When in AP mode for Orbi, any and all network traffic gets pass thru the system. If IPv6 is being pass from the host router thru the Orbi system in AP mode, then Orbi just passes this along to any connected client. There's no way to block it while in AP mode. This would need to be done at the host router level if that's possible. While in AP mode Orbi system doesn't manage or host IPv6 services. Just passes thru.