Ubuntu’s popularity often makes it the default choice for new Linux users. But there are tons of other Linux operating systems that deserve your attention. As such, I’ve highlighted some Ubuntu alternatives so you can choose based on your needs and requirements—because conformity is boring.
https://foundation.gnome.org/1999/03/03/gnome-1-0-released/
I really feel like you’re missing the idea of that sentence deliberately.
What Linux distribution came before Ubuntu that was specifically designed to be user friendly for a non-technical user?
There were a bunch of distros advertising ease of use; several were even sold in physical boxes (which was the style at the time) and marketed to consumers at retail stores like BestBuy years before Ubuntu started.
Here are four pictures of the physical packaging for three of those pre-ubuntu desktop distros designed to be user friendly and marketed to the general public:
Ubuntu was better than what came before it in many ways, and it deserves credit for advancing desktop Linux adoption both then and now, but it was not “one of the first” by any stretch.