There is a feature of darktable which is less known, although very powerful:
launching darktable with
--library [name of the library] can create a new/open a different library.
This feature is close to the catalogs in lr, and it's a pretty common scenario to have different libraries/catalogs (personal/professional photos, different clients etc.).
What would be a useful feature is to provide a UI (or a separate small tool?) to create/modify/delete such individual libraries, and launch darktable with the selected library.