Can't connect Google Mini to T-Mobile Home Internet

I am on the phone with them about this right now. I am using the Cycliner Router thingy.  The woman I am speaking with claims she is Level 3 Support (I have that number from a previous call).  However, she first wants to try and connect me to the 5Ghz band b/c she says by default the router is connected by default to the 2.4 Ghz band. But I am telling her I am set up with both by default - as I see in the GUI -- (i.e. this is how it came; I did no tweaking).  But this is odd b/c everything I have read on the internet says the reason we are having this issue with Wyze camera, Google Nest Mini speakers and Echo devices is b/c those devices need 2.4 Ghz (and not 5 Ghz).  I am getting the feeling that I am talking to someone who thinks she's is Level 3 Support.  Btw she just got back on line. She says that those devices are not supported. But a new firmware upgrade is needed.  I am not on the list to get that upgrade she says. My software/firmware ends in 0168.  That means according to her, that I am on the older one (relatively speaking).  From a conversation a week or so ago with a legit Level 3 Support, that gentleman said these newer routers (the cylinder ones) don't support much tweaking.  He suggested I use my replaced Time Capsule (apple world, speak) which I am currently using behind the T-Mobile Router for mac mini Time Machine backup and as a Gigabyte Switch, to control the 2.4 GHz band and set up those incorrigible devices to the Time Capsule. I am going to need my tech friend to come over for that. I am a knob.  I just sound kinda tech knowledgable, at least to me.  The purported Level 3 Support woman says she is going to call me back later. I will come back and report which she informs me.