Continue to get a message that my 2.4 ghz network is not available and I need access to it?

So I have approx 30+ devices that can only connect to 2.4ghz bands. Keeping in mind that most of the former (only 2.4) are light switches, outlets and light bulbs, they are dormant most times (I would assume). However I am getting consistent connectivity issues from this router since I started setting up the smart devices. I am working with a new AT T Router WiFi Router. The AT T installer suggested I “extend” my network but I don’t think that will fix my problem. Any suggestions? Would a mesh network do better? (Such as Google WiFi or Amplifi Alien)? My understanding is an extender - extends

Question by B Stacks on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.