I had followed @Mike_Maxwell’s suggestion to the fullest extent and believe me it has made a tremendous difference except for of course the Hue’s when operated thru ST which I do not believe is interference related in my case.
As an average user (although in IT but mostly dealing in finance/investment related s/w architecting, I am not an expert in networking).
But this is what I did with three AEBS routers (Two 6th gens and one 5th gen).
All the routers are on fixed channels for 2.4 GHz wifi which is 1, 6 and 11.
5 GHz is in auto mode (I should change this). They are all connected via Ethernet (Cat7 - because these are flat and shielded) and spread across the home on different floors (split level house) and is a roaming network. The entire Ethernet setup is cat7, the only reason being it is shielded.
Only the main base station provides the DHCP services and the rest are in bridge mode. All the hubs (ST, Harmony, Philips Hue, SONOS BOOST) MAC addresses are handed out reserved ip addresses by the primary base station/router to survive reboots of the router so as not to confuse ST and they get assigned the same ip. The lease period is set to 365 days.
The ST hub operates on Channel 14 and at a decent distance from any other hub or Sonos Play 1’s and BOOST. There are powered ST zigbee devices (motion sensors and smart outlets) spread all over the house.
The Philips Hue bridge operates on channel 25. The hues create their own mesh separate from ST zigbee mesh. So, do not count on the hues to make your overall zigbee mesh stronger. It won’t.
The Sonos BOOST is in the basement connected to one of the AEBS via Ethernet. This supposedly creates it own SonosNet network to which other Sonos devices connect. I don’t know how to check this as iOS does not expose this network. Android does. The basement mostly has all zwave devices mostly. The Sonos is kind of dicey to me as I am not sure about its impact.
Internet is always super fast for me in every corner of the house. All motion and contact sensors reacts instantly. Sonos responds 95% of the time using my own app when doors are opened or closed on a Sonos (Family Room or Bedroom) of my choice based on which mode I am in.
I have noticed that when I turn my Samsung Smart TV on, things get a little slower specially the notifications on the Sonos. So, there is definitely some interference there even though it is connected to the router via Ethernet. Same with Apple TV.
So, pretty much its the Philips Hues which I love the most works the worst with ST. It’s always the best performing when I use third party apps.