There is an updated pull request by sgn against master on the void-packages repository

https://github.com/sgn/void-packages python3-Sphinx-split-out
https://github.com/void-linux/void-packages/pull/17833

[WIP] python3-Sphinx: update to 2.3.1
- split out from python-Sphinx (2.x.x doesn't support python 2)
- despite their license looks like BSD-2-Clause, their README says it's a BSD-3-Clause
- python3-Sphinx doesn't depends on python3-setuptools (checked the code)

A patch file from https://github.com/void-linux/void-packages/pull/17833.patch is attached