My problem is: if I call https://graph.microsoft.com/v1.0/sites/{site-id}/drives/{drive-id}/root/children all I get are the top-level items of that drive.
https://graph.microsoft.com/v1.0/sites/{site-id}/drives/{drive-id}/root/children
I found that the below endpoint retrieves all files and folders in a library. The result will be paged, with a standard page size of 200 items.
/drives/{drive-id}/list/items