not from XA2 experience, but I was recently unlocking bootloader on mi pad 4 and flashing and what not..... On arch at the time. My device was always recognized and I could reboot it with adb reboot bootloader but then in fastboot mode with fastboot flash recovery xxx.img.......nothing. Forever "waiting for the device". And just because the second command needs sudo while 84639 instructions are all withot one.