Please explain this behavior. I create test poligon in VirtualBox - Ubuntu 16.04, MATE, Lubuntu, Xubuntu, GNOME, Kubuntu. the gtk3-audio-app is installed and works well. Only in Kubuntu the error appears Couldn't open libGL.so.1: libGL.so.1: cannot open shared object file: No such file or directory I shall add the line libgl1-mesa-glx in stage-packages? -- Best regards, vasilisc