LaTeX macros: how (best) to include them?

[lmoss]

I am stuck on several points related to LaTeX macros in Jupyter Books.
My main source for getting started has been the pages here, but I've also looked at some of the Sphinx pages.

I tried the suggestion in

https://jupyterbook.org/en/stable/advanced/sphinx.html#sphinx-tex-macros

and so my _config.yml file has the last 7 lines below:

sphinx:
config:
myst_enable_extensions: ["dollarmath", "amsmath", "colon_fence", "deflist"]
mathjax_path: https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js
extra_extensions:
- sphinx_exercise
- sphinx_proof
mathjax_config:
tex:
macros:
"N": "\mathbb{N}"
"floor": ["\lfloor#1\rfloor", 1]
"bmat" : ["\left[\begin{array}"]
"emat" : ["\end{array}\right]"]

But this doesn't seem to work.

For whatever it's worth, I also have

parse:
myst_enable_extensions:
- deflist
- amsmath

The second option on https://jupyterbook.org/en/stable/advanced/sphinx.html#sphinx-tex-macros
was to include lines in the beginning of a file, as shown below:

\newcommand\N{\mathbb{N}}
\newcommand\floor[1]{\lfloor#1\rfloor}
\newcommand{\bmat}{\left[\begin{array}}
\newcommand{\emat}{\end{array}\right]}

Now this did work for me 'locally', but not on Github-pages.
Do I need to change something on Github or on my workflow yml?

What I really would like to do is to include macro files both locally and on gh-pages,
and preferably to have just one addition for the book, not a few lines at the top of
every file, since I like to change macros occasionally.