I think Pug is the closest thing to Haml with traction: https://pugjs.org/language/conditionals.html

Here's a Pug -> JSX transformation: https://github.com/pugjs/babel-plugin-transform-react-pug

Detouring from the most popular path tends to come at the price of tooling idiosyncrasies that are rarely worth it, but it seems to at least work with eslint-react and has syntax highlighting in some editors.