Just an update on my previous Ethernet trouble with this same mobo and processor, Bory; I did a clean install of 10.12.6 following your guide to the letter (except I'm using on-board Intel graphics rather than nVidia drivers) and Ethernet is now working thankfully.
I previously also had USB 3 trouble - with no devices other than USB2 ones detected on front panel or back (main board) ports, and it's still the same now unfortunately. Wondering if you or anyone else could offer some advice.
There is power going to the USB3 devices I've tried (memory stick, external HDD etc.) because the light is showing on them, but it's not establishing a connection with the OS - nothing showing in diskutil etc.
Any advice appreciated.