A GNU/Linux distro can be referred to as an operating system. Not sure if you are memeing or not, but in conversation going into specifics about the GNU/Linux, or GNU plus Linux as you might like to call it, distinction, is not relevant here.

And in fact, I would say that saying that “GNU is the operating system” is even incorrect. GNU plus Linux is the operating system. Neither part by itself is a complete operating system.

So, the distro is the operating system.

Ubuntu is the operating system.