I can load booktabs from conf.py.
The current Sphinx doc here https://www.sphinx-doc.org/en/master/latex.html implies that this level of control is not available via conf.py, but there is a note at the bottom of the page that alludes to customization via templates:
As an experimental feature, Sphinx can use user-defined template file for LaTeX source if you have a file named _templates/latex.tex_t in your project. Additional files longtable.tex_t, tabulary.tex_t and tabular.tex_t can be added to _templates/ to configure some aspects of table rendering (such as the caption position).
and there is a parameter for pointing to it which I have set as follows in conf.py:
templates_path = '_templates'I added the templates from https://github.com/sphinx-doc/sphinx/tree/3.x/sphinx/templates/latex
The templates are not read.
Is this possible via templates? The feature introduced as experimental in Sphinx 1.6 and may have been dropped.