Orbi WiFi 6 Router AX6000 / RBR850 New Firmware V3.1.6.11_1.1.5

That is the FW that was available under ADVANCED, ADMIN tab and FIRMWARE UPGRADE.

If that is not showing, I would recommend a factory reset and subsequent setup where it should check for that.  (Sounds like you should do one anyway!)

The above is what I did (I actually took an extra step and factory reset AFTER the firmware upgrade just to ensure there were no hanging "chads")

I have to say, my AX is working now like a champ including the included RBS-850 sattelite AND two RBS-50 hardwired Sattelites as well that go to a separate building.

I have also found that the RBR-850 and RBS-850s have a MUCH wider range of coverage to wireless devices that under the old RBR-50 and RBS-50 were minimal signals... now they are maxed out.  Said another way, unless you have separate buidlings you want to cover, there may not be a need for the average home (3,000-5,000 sq/ft) to have additional sattelites.

Final note & lessons learned:  I had forgotten you have to enable remote management in the GUI before the app would let you do management outside of the LAN (e.g. WAN).

I had tried to hard wire to old RBR-50 in AP mode, but the system didnt like that, so I took the RBR out and replaced it with an RBS hardwired, and POOF, Bob's your Uncle!   Worked great.

The biggest pain so far is transferring ownership of the old RBR-50 to a friend of mine.   Why isnt transfer an online function for registered owners?