I'll highlight MyST which you briefly mention, as a way to get into Sphinx with markdown (with extensible roles+directives!)
Also, people who wish to write transformations on abstract doc trees, should also look at Pandoc filters (https://pandoc.org/filters.html). Pandoc perfected the same "abstract intermediate tree" philosophy that docutils follows, but handles a ridiculous number of input/output formats 🥇, and lets you write external filters in any language.
I'll highlight MyST which you briefly mention, as a way to get into Sphinx with markdown (with extensible roles+directives!)
Also, people who wish to write transformations on abstract doc trees, should also look at Pandoc filters (https://pandoc.org/filters.html). Pandoc perfected the same "abstract intermediate tree" philosophy that docutils follows, but handles a ridiculous number of input/output formats 🥇, and lets you write external filters in any language.