For converting notebooks to PDF with --to webpdf, nbconvert requires the Pyppeteer Chromium automation library.
Pyppeteer makes use of a specific version of Chromium. If it does not find a suitable installation of the web browser, it can automatically download it if the --allow-chromium-download flag is passed to the command line.
So, even if you use Firefox for browsing, you need Chromium to convert notebooks to PDF with this exporter based on Pyppeteer (--to webpdf).
You coud also try using --to pdf, which makes the conversion to PDF via LaTeX, but you should have LaTeX installed in your system.
Or you could try notebook-as-pdf (--to PDFviaHTML), but I think it is also based on Pyppeteer.
As stated in the documentation, https://nbconvert.readthedocs.io/en/latest/install.html#installing-chromium :
So, even if you use Firefox for browsing, you need Chromium to convert notebooks to PDF with this exporter based on Pyppeteer (
--to webpdf
).You coud also try using
--to pdf
, which makes the conversion to PDF via LaTeX, but you should have LaTeX installed in your system.Or you could try notebook-as-pdf (
--to PDFviaHTML
), but I think it is also based onPyppeteer
.