You’re probably aware of headcanons, right? Things which aren’t explicitly stated one way or the other in media, and so the audience must draw their own conclusions.
“Steve Rodgers is bi,” for example.
There’s never been a point in the MCU where he has expressly stated that he’s not bi.
(He’s totally bi…)
So the only argument that he’s not is heteronormativity.
Autistic headcanons, much in the same way, are rarely ever outright refuted in media.
(The exception being Sheldon Cooper, who constantly exclaims “I’m not crazy, my mother had me tested!” but even within the canon of the show, if you take into account his age, it’s not surprising that he would have flown under the radar for autism as a child.)
It’s just assumed that all characters are allistic.
Strangely enough, I’ve often found that characters who are never expressly stated as autistic (just coded as it) tend to be better written and more accurate than those who are given an on-screen diagnosis, though their lack of a label can often be used as a way to make fun of them without the backlash (again, Sheldon Cooper).
So, if you want to learn by example, autistic headcanons might just be the way to go.
Though, before you go scurrying off, I have a one more bit of advice.
Autistic headcanons are often… controversial.
Now, this could be a good thing for you. Polite discussions about whether or not certain traits are enough to consider the character autistic, could be educational.
But this is the internet. Polite discussion does not exist.
And, while two autistic people debating the veracity of a headcanon could be informative, an allistic person telling off an autistic person for their headcanon won’t be.
I go into the whole politics aspect in the video below.
So, as long as you’re mindful, here are some good places to start: