Qt doesn't get out much beyond Win/Lin/Mac.
Qt isn't available for enough platforms because it only runs on Windows, Mac, Linux, Android, iOS, Blackberry, Kindle, vXWorks, BSD, Solaris, Haiku, WebOS, OS/2, Tizen and AmigaOS? Anything that passes the "does it run on Amiga?" test is good enough for me.
You forgot qt in a browser: http://vps2.etotheipiplusone.com:30176/redmine/projects/emscripten-qt/wiki/Demos