The logo on the Discourse site links to the Discovery page.
I need to change this link to /categories, as this is the starting point I need everyone to use (as this is my specific usecase).
Is there a setting where I can change the link to which logo redirects ? - or - Can I turn Discovery page to Categories page?
Do you only want to change the link of the logo or which page is shown first in general? You can change the logo link with Custom Logo Link
And the first item in the top menu setting is the default homepage.
along with Moin’s post, the view is also affected by whatever you have for desktop category page style in your admin-all site settings. keep in mind users can override their own forum hompage in their user preferences under the interface tab.
desktop category page style
admin-all site settings
interface