Are there any sites that provide e-reader engine support charts for ePub, similar to what MDN provides for HTML?

Thanks for all the explanations. I always thought it was regular HTML, but now I know to watch out for the differences.

Can you say a few more words about the library https://github.com/standardebooks/tools ? Can it generate ePub3 from markdown files or do I have to feed it HTML already. Any repo with usage examples of the `--white-label` option would be nice.

Thank you, this was very interesting. I knew about XHTML in EPUB, but not that it was extendible - I had assumed it was mostly frozen.

Others have requested a list of features supported in different E-readers. i second this request.