Linux was made to run GNU software, and is borderline part of GNU. GNU, likewise, is made open, much like the Linux kernel, so it can run on anything.
I don’t know of any software designed for the Linux kernel that doesn’t also expect GNU.
Look, all I’m saying is that the two are very strongly bonded, like hydrogen and oxygen in a molecule of water. It would take a lot of energy to separate them. Adding to them is pretty trivial, there’s a lot of things that are water soluble by default, but without specific conditions and a lot of energy, they won’t seperate easily.
Honestly, I think the only OS I know of that’s the closest to being Linux but not GNU, is Android.