Lua is often used for that purpose. It is not a Lisp but it fulfills this role well enough.

This is getting pretty offtopic, but this is what GNU has tried to do with guile https://en.wikipedia.org/wiki/GNU_Guile

the ironic thing here is that Lispers fucking love sticking new DSLs wherever they possibly can. And I imagine most developers of these pet config files would argue the same thing. Unfortunately.

It was Microsoft of the 1990s that surprisingly brought some sanity to the table, with INI files. I'm glad tools like Git use this format.