OK, so I decided to look for myself, and I found
this Screen Rant article and
an article from Looper that both reference the MCU timeline book, which doesn't include anything from AOS, but according to the Screen Rant article there is a note from Kevin Feige where he says that there are canonical movies and series that are not included in the book because they don't take place in the Sacred Timeline. So this doesn't totally rule out AoS being canon, it just means it doesn't take place on Earth 616.