@David-TP 

Yes, tons. I have about 90 ish devices (smart home with tons of kasa switches and many other devices). Not all of those are 2.4, but the majority for sure. If I had to guess, I'd say 60+ are 2.4GHz.

But do note, if I kill the app, return to that feature and redo the scan, it figures out within a few seconds the "appropriate channel". So I don't think that's the cause. I've been able to do this regularly throughout my troubleshooting and I've seen this behaviour on other menus unrelated to the network optimization feature. But it's hard to pin point which ones... while struggling with other problems, I'd just kill the app and enable the option I wanted again and it would take.

I'm not going to be touching that channel just yet. Since I have no way to choose it, it's random and I don't want to risk breaking my other router I now have setup to transmit a separate 2.4GHz on channel 11 specifically because I can't manually choose the channel. If the Decos go to channel 10 randomly (which it often does), it then interferes with my other router. I've spent a lot of time messing around trying to pinpoint the issue 2.4GHz issues I'm having. It's definitely interference from neighbors.... but not much I can do since all channels are overloaded. Channel 11 is the best one available based on wifi scans I've done. But the Deco NEVER picks that one for whatever reason... it's like a hard coded limit of 10 somewhere. Or maybe because the channel width is 40MHz instead of 20MHz. With old router, I've selected 20MHz width and I'm able to choose channel 11 just fine and things just work.

If I do have to change things, I'll report the log as requested and repost here. It's likely in the next few days as I'm still determining the best settings for my home.

  @David-TP 

Just to be clear, as noted initially, this is a WIRED ethernet backhaul system. None of my 6 units do backhaul through wireless. So the 2.4GHz is reserved for clients only. But I don't know if somehow it still has a 2.4GHz backhaul active in the background.