Hope this experience helps someone who may be having issues. Sorry if it is a bit long but want to paint the right picture.
I have a ConBee using native ZHA integration to HA. It uses the deconz communication protocol but I am not running deCONZ & Phoscon apps except on a Windows PC when I need to change config parameters or do updates to the ConBee I’ll plug it in there and bring it up.
For some time I have been working with developers battling issues with the zigpy/zigpy-deconz component. At this point they have pretty much re-written the entire component and done a great job on it. One of the things that kept coming up was a lot off issues with devices going offline or becoming uncontrollable. One of the developers had a thought about radio interference with WiFi and asked if I could run a USB extension, which I already did. The question had me think about all my WiFi disconnections my router was experiencing though. Did some research and found the ConBee is by default on 2.4Ghz Channel 11 which overlaped into my router settings, not a very good thing.
Soooo… I pulled the ConBee and stuck it into my Windows PC and using Phoscon set the channel to 25 then put it back in my NUC, of course using appropriate shutdowns and startups for the system. The ConBee fortunately will stay where you set it even when removed from the USB port or powered off. Using a WiFi analyzer app on my phone I found a good spot for my 2.4Ghz WiFi control channel, used 7 in my case, and even with the bandwidth needed for 40Mhz it is still away from the ZigBee channel.
The result was much more than I thought… Many of the ZigBee issues cleared up, still some have a little work to be done but not because of radio interference. My router log is clean as can be, no more disconnects and reconnects every few minutes on the low band WiFi like there was.
If you are having ZigBee issues, not just with a ConBee, go check your router logs for WiFi device disconnects. You will also see WiFi issues in HA on the information screen if it is integrated to things like OSRAM Hub, WiFi connected TV’s and Reciever’s etc. that are experiencing WiFi network disconnects. If you are seeing these disconnects frequently try moving the ZigBee radio channel (if you can) and the router channel as far apart as you can. A WiFi analyzer app on your phone helps for the router setup to find a clean channel spot. Don’t use “Auto” channel select on the router it does not know about the ZigBee because they are not the same protocol but they do interfere with each other. I also use a USB extension to keep my Aeotec and ConBee away from each other and my NUC.
If you are having issues hope this helps, also hope this helps prevent issues for new setups. ZigBee and WiFi interference is a very real thing as I found out.