UEFI is in use. All ready since August. Did yesterday an `apt upgrade`. Computer reported after reboot: "no boot device found". The repair action was entering the hardware through pressing 'F2' during start. Add an UEFI boot device. Label name can be chosen freely. Boot file name is 'grubx64.efi'. Laptop runs now kernel version 4.18.0-2-amd64. Power management ( sleep / suspend / wake-up ) seems to have been changed. Cheers Geert Stappers