adding a 2nd 2.4 ghz router

The separate IoT Network on the 970 where you can set a 2.4Ghz only SSID name doesn't work? 

Can add a 2nd router connected in AP mode if you need to:

https://kb.netgear.com/31218/How-do-I-configure-my-Orbi-router-to-act-as-an-access-point and https://www.youtube.com/watch?v=H7LOcJ8GdDo&app=desktop

I agree with Furry....  Try using the IOT mode on the Orbi as that can usually connect devices that struggle with WPA3 protocols and/or 5 Ghz.   

IOT can be configured for devices that struggle with those issues without compromising your entire network.

I defaulted my 970 and started over again , I did make sure my IoT settings were for 2.4 ghz , I was able to add 2 more devices , My LG thinq and Nortiz Tankless hot water heater , and my Bose Soundbar , But ..... the Liftmaster Side mount garage door opener still wont go , it shows up during the procedures but it never gets to the point of wanting to join the loT network , I see on  youtube many people having same issues !  it worked on previous original Orbi from 3 years ago , I have also set up and tried " guest"  at this point I am stuck , I will call Liftmaster to see if they have any ideas , thanks all for the ideas , I was able to set up 3 mote devices with the loT  , just this one left .......