This is an interesting project! There's a lot of room for improvement in the self-publishing space!

I'm currently self-publishing a series of books about software development & it (https://dev-concepts.dev). As you've mentioned it is indeed quite complex to get up and running and generate beautiful output.

I've chosen to use AsciiDoc and created a template (https://github.com/dsebastien/e-book-template) based on Matt Raible's work for InfoQ books (https://github.com/mraible/infoq-mini-book). It's far from perfect, but it's a good starting point.

My first book was published by Packt, and I also used Asciidoc for the initial draft, but then had to switch to their wordpress-like platform, and it was a real nightmare to use. Being able to use Asciidoc end-to-end feels so much better.