I am new but wanted to share the following information. I installed 19.07 RC2 on Gl-x750 and had issues getting to USB-Port working. Support of Gl.inet advised that it is necessary to modify gpio pin 2. For me the following worked:
echo 2 >/sys/class/gpio/export
echo out >/sys/class/gpio/gpio2/direction
It might be either implemented into the build or placed on a device page which is not yet available.