Free but uninstallable CAT6 has some uses. I've seen quite a few street artists use the thin copper wires to make art, usually jewelry. But with 400 ft, I could see some art or construction projects that make use of it as a physical not electrical product.

It would be perfectly safe to run in a conduit or to bury. It's just not rated to run between floors, but was stamped saying it was. My home is single story, and I mentioned that during the recall process, but the process was rather rigid...

What does "the process was rather rigid" mean? Couldn't you just decline? (Although maybe it wasn't even safe for your use.) But then, I don't even understand why it would be safe to run except between floors.

Also, did you try pushing back on the replacement worker's work? It's a bitch to do, but I've gotten companies to either redo their handyman's bad work or just let me choose a vendor (which I would ask for after the 2nd time he showed up.) Stapled Manhattan distance wiring is not the same as diagonal through the dirt.