From what I have found, there is no way to change the Zigbee channel when using the ZHA integration in Home Assistant. I’ve seen multiple posts saying it’s hardcoded to ch15, but I haven’t seen that officially confirmed and I haven’t rummaged through source code myself.
I understand that Zigbee ch15 is between WiFi ch1 and ch6 (and can likely coexist there), and that setting your WiFi to be on ch11 would keep WiFi and ZHA Zigbee from interfering entirely. Reference: https://www.metageek.com/training/resources/zigbee-wifi-coexistence.html
However, that solution won’t always work. I’ve been trying to figure out why some of my Zigbee devices are intermittently not responding reliably. The devices in question are mains-powered devices (light bulbs and strips) that usually work great, but sometimes they fail to turn on/off or set their color/temperature/brightness correctly. I’ve discovered the for some reason, one of my neighbors’ routers has decided to park itself on WiFi ch3 recently - a different WTH topic, but not for here… I don’t know how much WiFi bandwidth he’s using on ch3, but ch3 is right on top of Zigbee ch15. It could explain a lot, and I’d like to test that theory.
I’d love to be able to try moving my Zigbee network to Zigbee ch20 or ch25 (like my Hue Bridge has already done), but I haven’t found a way to do that in ZHA.