ahh (
doh! - homer simpson impression), I forgot to tell you to
uninstall the Realtek audio drivers first, reboot and then try to re-install the Realtek drivers using the hdxrt.inf file in Device Manager. my bad.
perhaps this is why I always remove/uninstall existing Realtek audio drivers before installing new ones. Otherwise, when installing new drivers repeatedly over old ones in Device Manager, one can end up with old & redundant Realtek HDA drivers that take up a lot of disk space in the Windows driverstore folder - take an example from
this guy (he had lots of nVidia drivers & Realtek drivers installed and had to remove the old & redundant ones using DriverStore Explorer)
so my trick does work but requires uninstalling the Realtek HDA drivers first (either thru Programs & Features if the Realtek HD Audio software is listed there OR by selecting it in Device Manager, choose Uninstall but also check the option
Delete the driver software for this device), then after restarting the computer re-install them in Device Manager by choosing the HDXRT.INF file.
It looks like I will still use the traditional Realtek HDA drivers on my friend's ASUS motherboard for a few more months. By the time the Win10 v1809 (RS5) release comes out, I will permanently remove those drivers and switch to the newer & smaller Realtek UAD drivers which will allow using the Realtek audio console UWP app from the Microsoft store