Ok, I suggested adding python3-sphinx explicitly, but my tests indicate that python3-sphinx-rtd-theme is also required after all.
I think you need this: - python3-nbsphinx <!nocheck>, + python3-nbsphinx, [...] - python3-sphinx-rtd-theme <!nocheck>, + python3-sphinx-rtd-theme, and maybe something more, but I didn't go as far. Thanks.
