GL.iNet Beryl (GL MT1300) - Not working wifi built in

[Borromini]

That sounds like a calibration data issue. I believe the MT1300 is MT7621 based. Is yours using NAND? Bad blocks can shift addresses and break wireless because of that. See this topic e.g.:

Netgear R6850: very low transmit power on 5GHz

I'm going out on a limb here, but that data seems to be extracted from flash at boot time. It's expected at a certain location that is predefined in your device's DTS. I have an R6800 (all MT7615 wireless) and EEPROM is read into /sys (a virtual filsesystem): # find / -name "*mtd-eeprom*" /sys/firmware/devicetree/base/pcie@1e140000/pcie@0,0/wifi@0,0/mediatek,mtd-eeprom /sys/firmware/devicetree/base/pcie@1e140000/pcie@1,0/wifi@0,0/mediatek,mtd-eeprom I don't know if you could try overwriting an…