Supportive tech forums & online communities: Any recommendations?

Over the years I've benefitted a lot from different online communities that I've stumbled upon.

I am currently putting together an article on the best online communities (slack channels, forums, etc) which beginners can join (in my case, specifically for learning cloud and AWS).

And I know there's a lot of great different communities out there—sometimes the smaller, hard to find ones are the best.

Are you part of any great software communities that are active and supportive that you'd be willing to share?

And of course... I know about DEV.TO!