It seems that what are called Communities/Groups on Skool would translate to Categories in Discourse.
So you’d have a “All categories” view like Skool’s landing page:
And a topic list view for each category like this:
I wonder if the look & feel is such a determining factor though. It seems what sets this apart is more the functionality to host a platform that allows members to open groups and administer and moderate them themselves. To implement this on Discourse you’d need to extend and develop some features with plugins. Rather than change the look.