The nginx-related files are used by pydrake.geometry.SetupMeshcat() to
configure a Deepnote notebook to allow for MeshCat traffic to flow.  Refer
to the implementation in bindings/pydrake/_geometry_extra.py for details.

The xvfb-related files are used to launch an X display suitable for Drake's
image rendering simulations.

Even though these files are used on Ubuntu- or Debian-based systems,
we don't place them under drake/setup/ubuntu/... because they are not
relevant to most Drake users on Ubuntu -- they are only useful for the
Deepnote cloud hosting platform.
