Country DE breaks wlan // Xiaomi Redmi Router AC2100

[lleachii]

This issue was similar:

Radio0 "Device is not active" (Qualcomm Atheros QCA9886 802.11acn)

I had exactly the same issue. For me worked setting (using LuCI) Country code to "00 - world" in Advanced Settings tab of the Network Settings followed by the restart of the radio0. Hope this helps!