I've found JavaFX's scenegraph approach rather neat. Effectively it borrows from HTML, but where the basic node set is designed to be UI elements rather than co-opting a set that was designed for text documents. It seems to take a surprisingly small amount of code to sketch up an interface.

React's not bad on the web side (especially with Scala.js) but fudging around layouts in components with divs and Bootstrap still feels clunky.