Using manjaro linux, DE: kde. Zoom and scrolling work well, i can perfectly draw at scratchpad and tablet tester, but can even do dot at file. Nothing changes with enable touch painting.
Does touch work in the tablet tester? Settings->configure Krita->Tablet Settings. Because otherwise that means Krita just doesn’t even get the touch events to begin with…EDIT: If Krita was build with qt 5.12, it might be that mouse events do not register, this is a bug with both Krita and qt in combination. Your touch screen might be registered as a mouse event, and that means that right now you’d need a version of Krita that uses qt’s xcb implementation, but the only easy way to get that is to build Krita yourself.