I have tried the stable build 18.06.1 for Archer AC2600. First, I set the 5 Ghz channel to Auto, and it sets to channel 36, the lowest and also the most crowded channel in my place. I tried to change it to other channels, but it makes the 5 Ghz SSID disappear. I need to reboot a few times to make it reappear, but it revert back to original channel 36.
Just in case, give it time to settle before declaring it failed. The router must listen passively to DFS channels for a minute to search for DFS events before it is allowed to start transmitting.
There is nothing "magic" about "auto" -- as far as I know it just picks the lowest authorized channel. You're generally better off selecting an open or less-crowded channel yourself, with the caveat that DFS ("radar detection") may push you off of it, as it is required to do in most jurisdictions.
I have waited for it to appear, but it did not. I think my place did not welcome DFS channel. I will stick with channel 36. Thank you guys for your help!
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