My problem that I find is that mobile, consoles, TVs, car entertainment systems, watches, and so on all need fairly distinctly different UIs from desktop and if

My problem that I find is that mobile, consoles, TVs, car entertainment systems, watches, and so on all need fairly distinctly different UIs from desktop and if you have to redesign the entire UI for them anyway, then why not do it in a native system that handles them well. Odds are most of the heavy lifting will either be fairly trivial or done in a separate back-end be it on a server or locally. At that point it doesn't really matter what you write the front end in as long as the back-end has a decent API. Also quick edit: A number of car dash UIs do actually run on Qt and Qt does support mobile but Qt does its own compositing instead of the OS.