Issues setting up Orbi in AP mode alongside Nighthawk X6

Actually, I figured it out and got it working. I managed to connect to the Orbi admin web console by turning off Wi-Fi on my laptop and connecting to the Orbi router via Ethernet cable. It turns out the Orbi was still setup in Router/AP mode, and it had its own fixed IP address at 10.0.0.1, whereas my Nighthawk router was at 192.168.1.1. That is why I could not load the admin web console when I looked it up in the IP table of the Nighthawk.

So I managed to update the firmware on the Orbi and the two satellites, and then set the Orbi router in Access Point mode only (no router). Once that was done, the Orbi got its IP address from the DHCP server on the Nighthawk and I can still manage it by looking-up its IP in the Nighthawk IP assignment table. Furthermore, I left the Orbi on the same SSID as the 5G network on my Nighthawk, which means I can now roam all over the house on the same SSID.

I benchmarked it using a Speedtest app in all the remote corners of the house - especially those that used to be problematic - and I now I have awesome Wi-Fi everywhere. Love it!