macOS doesn't currently have Nvidia drivers from this generation (from what I remember). It supports a handful of mobile cards and no more, which is the extent to which Nvidia has been implemented in Apple computers as of late.
Meanwhile, the past few generations of graphics gear in Apple computers has been a pretty wide range of AMD stuff. Vega, Polaris, FirePro have all been represented in the last 5 or so years. All they had to do was modify the driver to be able to read from the TB3 PCIe device rather than just an internal one.