How can I hide all subcategories from homepage?

[Heliosurge (Dan DeMontmorency)]

You may want to look at this theme component.

Category Hider Theme Component

Hi all, I’ve created a simple theme component. I hope this could be of use for some! Overview This is a theme component that allows you to hide specific categories from either the hamburger menu or category boxes. Why would you need this component? If your discourse website has a lot of categories and you would like to hide some from appearing in either the menu bar or on the main page, this component can be helpful. Screenshots Preview of Hambur…

I think it will.do what your looking for.

There are also site settings that affect how categories are displayed and othet theme-component like Modern Category Boxes.