Comment 2 for bug 1579265

Unfortunately Qt WebEngine is not available at all in Debian or Ubuntu, because it's largely unsuitable for distribution. This bug therefore won't fix until there is someone willing to spend considerable effort (months at minimum) to package Qt WebEngine to Debian (from which it will get into Ubuntu).

Some discussion pointers from last years at:

http://lists.alioth.debian.org/pipermail/pkg-kde-talk/2014-October/001970.html
http://lists.alioth.debian.org/pipermail/pkg-kde-talk/2015-April/002047.html
http://lists.alioth.debian.org/pipermail/pkg-kde-talk/2016-January/002289.html