A minimal not-working example:

from pathlib import Path
import polars as pl

Alphas = pl.Enum(["hello"])
MiniStruct = pl.Struct({
  "alpha": Alphas,
})
MiniStructs = pl.List(MiniStruct)
df = pl.DataFrame(
    pl.Series("xs", [[] for _ in range(1)], dtype=MiniStructs)
)

path = Path("xs.arrow")
if path.exists():
  path.unlink()

df.write_ipc(path)

Produces:

thread '<unnamed>' panicked at /home/runner/work/polars/polars/crates/polars-arrow/src/array/list/mod.rs:82:61:
called `Result::unwrap()` on an `Err` value: ComputeError(ErrString("ListArray's child's DataType must match. However, the expected DataType is Struct([Field { name: "alpha", data_type: Dictionary(UInt32, LargeUtf8, false), is_nullable: true, metadata: {"POLARS.CATEGORICAL_TYPE": "ENUM"} }]) while it got Struct([Field { name: "alpha", data_type: Dictionary(UInt32, LargeUtf8, false), is_nullable: true, metadata: {} }])."))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

PanicException                            Traceback (most recent call last)
/tmp/ipykernel_264688/3257874384.py in ?()
     13 path = Path("xs.arrow")
     14 if path.exists():
     15   path.unlink()
     16 
---> 17 df.write_ipc(path)

~/bumblebee/.venv/lib/python3.12/site-packages/polars/dataframe/frame.py in ?(self, file, compression, future)
   3251             issue_unstable_warning(
   3252                 "The `future` parameter of `DataFrame.write_ipc` is considered unstable."
   3253             )
   3254 
-> 3255         self._df.write_ipc(file, compression, future)
   3256         return file if return_bytes else None  # type: ignore[return-value]

PanicException: called `Result::unwrap()` on an `Err` value: ComputeError(ErrString("ListArray's child's DataType must match. However, the expected DataType is Struct([Field { name: "alpha", data_type: Dictionary(UInt32, LargeUtf8, false), is_nullable: true, metadata: {"POLARS.CATEGORICAL_TYPE": "ENUM"} }]) while it got Struct([Field { name: "alpha", data_type: Dictionary(UInt32, LargeUtf8, false), is_nullable: true, metadata: {} }])."))