The solution, found buried in XDA and Russian 4pda forums:
The driver is not a generic ADB (Android Debug Bridge) driver. It is a low-level interface driver that allows communication with the device when it is in (port 900E) or Qualcomm HS-USB QDLoader 9008 mode. sdm439-qrd usb driver
Additionally, unauthorized use of the SDM439-QRD driver to circumvent FRP may violate local laws regarding device ownership. Use only on devices you own.
You can find official installers at sites like Qualcomm USB Driver or GSM USB Drivers . The solution, found buried in XDA and Russian
stands for Qualcomm Reference Design . It’s a standardized board that OEMs use to jump-start their own devices. The QRD variant of SDM439 comes with pre-defined peripherals, power management (PM8953/PMI8940), and crucially — a fixed USB configuration used for debugging, flashing, and factory testing.
