Maybe Quora?
maybe you can post the question in all such communities you know (and those that'll be suggested here), and also turn it into a test - which one will give the best answers, with best signal/noise ratio?
I'm interested in learning more about existing ML model capabilities, and in particular how easily a model that is used on one task could be used for another, similar task.
For example, if I want to know and/or estimate whether an existing AI system like AlphaZero could beat Angry Birds with current capabilities, what's the best place to post that type question?