Notebook to PDF converting forces markdown title numbering

[VasoVV]

Description

Converting a notebook with titles in the markdown sections to PDF adds odd numbering to all titles.
The quickest way to disable this feature is to append {.unnumbered} / {-} attribute to the title row, but they are visible in the notebook.

All other methods, such as using custom LaTeX templates, are painful and do not work.

Reproduce

1. Create a new Notebook
2. Add two markdown sections
3. Create simple titles
4. Export to PDF via File / Save and Export Notebook As / PDF
5. The PDF contains titles with the numbering

Expected behavior

Numbers must be where I put them.

Context

• Operating System and version: Linux Ubuntu 24.04
• Browser and version: Latest Chrome and Firefox
• Jupyter Notebook version:

jupyter --version
Selected Jupyter core packages...
IPython          : 9.5.0
ipykernel        : 6.30.1
ipywidgets       : not installed
jupyter_client   : 8.6.3
jupyter_core     : 5.8.1
jupyter_server   : 2.17.0
jupyterlab       : 4.4.7
nbclient         : 0.10.2
nbconvert        : 7.16.6
nbformat         : 5.10.4
notebook         : 7.4.5
qtconsole        : not installed
traitlets        : 5.14.3

Tested in the clean Jupyter installation in the dedicated venv.