It doesn’t have to be super advanced, just basic stuff like square wave, noise, maybe triangle. Simple enough so everyone can understand it.
The only one I’ve found, this one, was made for relatively old Unity (3.5) and since we had since then Unity 4 and 5, it is hardly relevant and most likely deals with lots of obsolete/removed functions. It also deals with more advanced generation such as FM synthesis which is a bit overwhelming for a newcomer.
TL;DR: I’d like to see tutorial that deals with most basic sound generation (NES or even PC Speaker grade) so it can be easily understandable.