The key idea of soupault is that it works on the HTML element tree level and can automatically call external convertors on pages (based on page file extensions, see [1]), so the input format doesn't matter to it.

You can bring your own convertors and pass any options to them. I'm not saying it's a perfect SSG for everyone, but at least uncommon input format support isn't an intractable problem for it.

[1] https://github.com/dmbaturin/soupault-website/blob/master/so...