How to run Discourse in a subfolder?

I want to run Discourse on a subpage like mydiscoursedomain.com/forum. The domain is clean, meaning it only has discourse on it.

Usually I would have a something like a www directory with an index.html where I would add my subpage etc.

How should I approach this?

The best approach is to use different subdomains for the two sites, but you can also see Subfolder support with Docker.