On the "Writing plugins" page of the documentation the section on Making your plugin installable by others is not quite right. It states that the recommend way to register pytest11 entry-points is to write:

[project.entry_points]
pytest11 = [
    "myproject = myproject.pluginmodule",
]

but since pyproject.toml here is set to use Hatchling it should actually be (source):

[project.entry-points.pytest11]
myproject = "myproject.pluginmodule"

The sample pyproject.toml also includes the lines:

[tool.setuptools]
packages = ["myproject"]

which I doubt are needed.