Do not try to upgrade directly as a sysupgrade image from the GL-Inet software, even from luci over in advanced... Installing sysupgrade will likely result in a device that can't talk - it's not bricked however, uboot recovery can get things back up and running...

qualcommax: ipq60xx: add GL.iNet GL-AX1800/AXT1800 support
    
    Specifications:
      SoC:     Qualcomm IPQ6000
      RAM:     512 MiB
      Flash:   128 MiB NAND
      ETH:     Qualcomm QCA8075
      WLAN1:   2.4GHz 802.11b/g/n/ax 2x2
      WLAN2:   5GHz 802.11a/n/ac/ax 2x2
      Button:  Reset, Switch
      USB:     1x 3.0
      SD slot: 1 in GL-AXT1800
    
    Install via stock firmware:
      Upload factory.bin in stock firmware's upgrade page,
      do not preserve settings.
    
    Install via uboot web failsafe:
      Push the reset button for 5 seconds, then use broswer
      to access http://192.168.1.1, and upload factory.ubi.
    
    Afterwards upgrade can use sysupgrade image.

factory.ubi from u-boot recovery works fine for first flash over from gl-inet firmware.