equvalent for package_data and data_files ?

[parmentelat]

I am transitioning some old setup.py-based projects to pyproject.toml and for now I have been using hatchling as a build tool

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

I am facing the issue of translating to hatch 2 constructions that were supported previously with setup.py:

• package_data : typically to copy over some stuff under the package installed repo
• data_files: typically to install stuff at some completely other location - think /etc/ or similar

I have read about dealing with the first category using this in pyproject.toml

[tool.setuptools.package_data]
myPackage = [
   "rel/ative/paths"
]

I have played with that, but with mixed success; with some of my projects this works fine but with some others not, with no apparent difference between the 2 use cases
also, about data_files, for now all my attempts have failed with this one

So I guess my first question is maybe just this:
when opting for hatchling as the build tool like I did, can I still leverage these 2 setuptools features like I am trying to do ?
my first understanding was that not, but maybe the answer is more complex than just yes or no, does it depend on other settings ?

I feel like I don't have a clear understanding of how this is supposed to be used...