It’s likely that your homepage default is controlled by the top_menu site setting. Here’s how to fix it:
- Go to your site settings and search for top menu.
- Make sure the first item in the list is categories (e.g. categories|latest|new|unread…).
- Discourse uses the first entry in this list as your homepage.
- If latest is first, it will always load the “Latest” page by default.
- After updating, save changes and reload your homepage.