An older thread, but a new experience. I asked AtHom about the option to change the Zigbee channel on HP23, but they told me that option will not be added. Very disappointing. I had done his in the past to get a clear chnnel on Doconz and most devices switched without too much issues. A Homey backup/restore contains the zigbee channel so hat did not work. 
The only “solution” for HP23 is to reset the zigbee network (repeat until the desired channel get selected). Luckily it turns out that you can then repair all broken devices and at least still have functioning flows and insights after you are done.
It took me about an hour to reset 60 devices all over the house (mainly Aqara sensors/Tuya plugs/Generic Zigbee bulbs), but I am now up and running again on a new channel with hopefully less issues due to interference during the busy evenings. 
