I think what you're looking for is not "copyrighted material" but material that's both 1) used without permission and 2) outside the scope of fair use.
There's no easy answer there, hence New York Times v. OpenAI.
There's no easy answer there, hence New York Times v. OpenAI.
I think sticking a straw in Zlib or AA or LibGen or whatever it is, and drinking until it makes gurgling slurping noises as it hoovers up the dregs at the bottom of the barrel, is far, far removed from “fair use”.