It seems that createEnumType is wrongly typed as:

def createEnumType(
    self,
    datatype: np.dtype[np.integer] | type[np.integer] | type[int],
    datatype_name: str,
    enum_dict: Mapping[str, int | np.integer],
) -> EnumType: ...

But e.g. datatype="u1" is also supported.

• the version of the software with which you are encountering an issue: netCDF4==1.7.2
• environmental information (i.e. Operating System, compiler info, java version, python version, etc.): Win10 / python 3.12
• a description of the issue with the steps needed to reproduce it:
  downstream issue:
  Mypy 1.12 issues pydata/xarray#9624

problematic lines (roughly):

with nc4.Dataset(tmp_file, mode="w") as nc:
    nc.createEnumType("u1", "cloud_type", {"clear": 0, "cloudy": 1})