Apart from being open source what is Linux? Could I not create my own operating system that is different to windows or Macos and call it Steve, again there might be an awnser for this and sounds stupid but its more out of curiosity.
It is. The other person is confusing it with Solaris, which is a Unix derivative based on a mix of System V Unix and BSD.
Linux is a Unix, but Unix is not Linux. Solus is a Unix, as is MacOS (a really bad one), and BSD.
I’m pretty sure Solus is a Linux based OS, at least according to Wikipedia:
Solus (previously known as Evolve OS) is an independently developed operating system for the x86-64 architecture based on the Linux kernel and a choice of Budgie, GNOME, MATE or KDE Plasma as the desktop environment.
linux is often called a unix but it is only unix-like. It’s not officially unix cerrified the way macos, hp-ux, and others are.
It’s possible to certify Linux as “an official Unix”, evidence: https://en.m.wikipedia.org/wiki/EulerOS That particular Linux distro’s Unix certification has expired, though.