I write in GitHub flavored markdown (so that is readable on GitHub and I can reuse parts for my blog, etc). I use pandoc to generate pdf/epub versions [0] and mdbook to generate web version [1]

[0] https://learnbyexample.github.io/customizing-pandoc/

[1] https://github.com/rust-lang/mdBook

Technical book writers seem to gravitate toward Latex or Microsoft Word.

Just ms word for me

I write in Google Docs mostly for the collaboration features. It's super easy to invite someone to leave comments. I use the Code Blocks add-on to format code. When it's time to publish I use the DocsFlow plug-in to import the doc into InDesign for typesetting.

Use Kindle Create (available for Windows and MAC) for selling on Amazon.

I use HTML but it's not the best. Latex is probably a better option.

Is LaTeX still a good choice for "modern" ebooks? Do folks still want PDFs?

if i don't see a pdf, i don't buy it

Why is that, if I may ask? Do you print all your e-books? I find PDF to be an inferior format for consumption on a screen.

I was the same way, but epubs can be quite good now, even for highly formatted technical content.

May depend on your market, it amazon sells the vast majority of ebooks in the world.

So, neither of those.

org-mode, if you don’t mind using emacs.

I recently had to print some of my notes - already in Org mode - for a meeting. After going through numerous options including reformatting in LibreOffice, pandoc, HTML, etc etc I discovered that org mode can export the documents to PDFs that look better than anything else.

Unfortunately, I don't have the config options that I used any more! I changed some fonts and drastically reduced the margins. And some places in which underscores were used had to be escaped as the PDF export interpreted underscores as being subscript.