Additional information: Same computer, booting from: openSUSE-Tumbleweed-DVD-x86_64-Snapshot20190327-Media.iso om a usb stick and selecting menu item "Upgrade" results in the same grey screen after the RAM image is loaded. Booting from: openSUSE-Leap-15.0-KDE-Live-x86_64-Snapshot20.168-Media.iso works perfectly.