No basically all Linux uses gnu Coreurils as a foundation and is therefore best called gnu+Linux. There’s a great RMS rant about this , it’s what the title is referring to.
They should make a new version of Linux from scratch where all you get is the Linux source code and you write the compiler and core utils yourself. Now that would be Linux.
Aren’t their embedded systems that run the Linux kernel without the core-utils (maybe with busybox instead) and would therefore be non-gnu linux variants?