Ok, on #libreboot, no one is able to answer me, besides the the info that
this board has not been fully tested yet.
Lilos posted a thread (closed now, very practical) about several issues, like
not being able to boot with 2 CPUs, USB keyboard not working, the PC not
booting from the GPU ("fully" supported by Nouveau, I checked), and the HDD
not recognized.
So I have no idea if updates since may solve these issues or not.
So it's safe to say: don't purchase for now.
I have one, but now I really hesitate in purchasing the rest of the hardware
until I have more info.
This sucks, hopefully it will end up being a worthy investment.