Well that’s the funny thing : it’s ok they are showing in dom0, but the VGA part was showing (an is stil lshowing) with nouveau driver when I actually blacklisted it 
I removed the pci-hide from Grub, but still, nouveau is supposed to be blacklisted and… it seems it still somehow ‘captured’ by the Nvidia card before it is actually blacklisted… Although, a grep nouveau with the dmesg doesn’t show anything…
And the BIOS of my laptop contains so few information, even the ctrl+s doesn’t show much more and noting on about the graphic cards…
Not sure how it plays between the Bios, Qubes and the Hardware… My luck is it works, but I understand it could be very frustrating since there doesn’t seem to be a ‘root cause’/ reason for this to work… Or not…