Spectrum wifi signal keeps dropping (IPV4 vs IPV6 Issue???)

Laptops: MacBook Pro, running BigSur 11.6, Dell, Levono and Chromebook

Phones: iPhone 12 and 12 Mini (Verizon Network) and Samsung Galaxy

We recently changed our ISP to Spectrum (from ATT). We are using the modem and router that they gave us. For a few months everything worked fine, but recently we have had trouble with intermittently losing the connection to our wifi network whenever we use our phones or laptops. (This doesn't happen with the Samsung SmartTV, our Alexa Echo Dot or the Roku devices). I work from home (Macbook Pro) so this is a REAL problem especially for me.

I have tried resetting every device, and called Spectrum. They "reset" something on their end, but that didn't help either. When we were with ATT, we could see 2 frequencies on our network, one was 2G and one was 5G. But now, with Spectrum, we only have one frequency to use. It seems that this router is somehow "smart" and knows which devices work well with which frequency, and automatically selects them on its own?? But, when my laptop connection goes out, and I look under the "network" tab, there is a long string of numbers and letters in place of where I would traditionally see the router's 9 digit IPv4 address. (Is this an IPv6 address?) Well, evidently my laptop doesn't like it. When I turn the wifi off, and then back on again, it reconnects using the 9 digit IPv4 address, and works for a while again - sometimes for 30 - 45 minutes, but sometimes only for a few seconds. Same with my iPhone 12 mini.... it periodically stops working, I toggle the wifi off and back on again, and then it works again - for a while.

The other members in my household use Windows based laptops and say they have also had the same kind of issues. (Also with the other iPhone 12's)

What should I do?????