As all you can see there are 6x risers are going from MB - so it is standard one, but additional are connected through PCI splitter. And how to get them married together - it is his know-how.
And this is why it can be done only under *nix system
Just buy it - you cannot make it

its probably a Z97 gaming 5 MSI board = 7 PCIE slots - 7 GPUs
with one M.2 to PCIE ? - 8th GPU
and ubuntu should work fine.... dont need to waste money on a ubuntu wrapper
that is exactly what this rig is. I have one just like it.