Not working as of 19.07.7. My device is Newifi D2 which uses the MT7621 chipset.
Some Team Group USB 3.0 flash drive works fine. Seagate external HDDs do not work. I have no choice but to use a USB 2.0 cable to force it to work in 2.0 mode.
Update 2021-09-10: works p̵e̵r̵f̵e̵c̵t̵l̵y on 20.02.0 now. Edit: the driver is USB3.0 but not UASP. Better than nothing though.