you might want to take a look here :
GL.iNet Beryl (GL MT1300) - Not working wifi built in
OpenWrt on MT7621/MT7615N devices with 5GHz problems
you might want to take a look here :
GL.iNet Beryl (GL MT1300) - Not working wifi built in
OpenWrt on MT7621/MT7615N devices with 5GHz problems