I use Lenovo U530 Touch laptop with multitouch screen, and Krita sketch does not receive touch events. I tried some demos using Qt5 QtQuick 2 MultiPointTouchArea, and they work well, all ten touch-points are handled correct. Probably, if Krita sketch uses Qt4 QtQuick MouseArea, mouse click event would not be invoked by touch. Reproducible: Always
Well, we do use Qt4 still, but we're enabling touch events in the view. I haven't checked recently with Kubuntu on one my test laptops though -- I'd need reinstall for that.
Marking as duplicate of 342005 which is broader in scope. *** This bug has been marked as a duplicate of bug 342005 ***