I've a set of Sphinx topics online
Themes and customization
- How to create a custom landing page https://ofosos.org/2018/12/28/landing-page-template/
- A tour of the Sphinx Read the Docs theme https://ofosos.org/2019/03/26/a-tour-of-the-read-the-docs-sphinx-theme
- Integrating doctests with Travis https://ofosos.org/2019/01/06/doctest-travis/
- On Opensource.com you'll find an article about building custom workflows in Sphinx https://opensource.com/article/18/11/building-custom-workflows-sphinx. This also spawned some work in Sphinx itself.