@zonggestsu Thanks for your comment!
I have already applied udev rules as suggested in the link you provided. As I explained, if I enter the upgrade mode by pressing power + reset key before starting the VM, the linux guest OS detects the Amlogic USB VID and I could successfully flash the uboot via pyamlboot script. Doesn’t it means the VIM3 is communicating with the PC? But after this step, fastboot does not show any devices and stuck saying that <waiting for any device>. Is additional steps requried to make the device enter the fastboot mode or unlock the bootloader? I can’t find any other instruction eve in link
I downloaded the AOSP and bootloader as suggested in this.
In addition, the VIM3 is connected with PC using single USB-C cable. Should I seperate the power and the data cable?