I see your point. Having the mobile layout Grid thing is quite handy. There is another toolkit for React I've been using for an admin backend that has proven useful, not quite as polished but has more of a complete toolkit for what I need. npm rebass, relfexbox, react-geomicons was on Hacker News as well -> http://jxnblk.com/rebass/
That's nice but their idea of grid is to hand you a bunch of fixed-sizes CSS you can slap on elements. That has very little to do with the actual layouting a UI toolkit like Qt provides for.