I'm honestly not sure, and I spent some time checking that on #Wikipedia before I posted.
But tentatively, I believe ICANN is the only "landowner" so-to-speak, which rents out in bulk to the various wholesale/resalers, who in turn handle retail rentals.
... I think.
In the process, I did discover the existence of OpenNIC ... https://en.m.wikipedia.org/wiki/OpenNIC
Now trying to figure out how useful they are.