Dear maintainers, I re-checked from BIOS settings and finally found that I had ignored GNOME sound setting source even when I checked sound tests.
It was set onboard S/PDIF, instead of dGPU HDMI. Changed it to the GP108's HDMI, it's okay; clear sound from GeForce 1030 HDMI output. It was clearly my fault. I am sorry again. However, the initial value should be HDMI-output, when video output is only HDMI, I think. if (video_output == HDMI-only) initial_sound_source = HDMI-sound; something like that. Of course on board HD audio S/PDIF would be better and many people might prefer that, use that. I am not familiar with S/PDIF. SUMMARY ======= * Kaby Lake (Z270) + GeForce 1030 with nouveau works. * GDM, GNOME, Firefox, playing on Youtube, are OK. * lm-sensors asus-isa-000 reads wrong. It just reports cpu_fan only, and the value is 0. On BIOS and visual, It is rotating. * I enabled ALPM on BIOS, since the kernel now support that; there are no-data-loss by now. * byobu, after all, seems works both on CLI and GUI. I cannot find specific log and reproduction method. * LibreOffice, Google Mozc, and Japanese inputs are OK. * AppArmor working. * Thunderbird reads local delivered logcheck summary mails. I will re-install the next week Buster image, and install Stretch and dist-upgrade, when I have time. Thank you for reading messy reports. Thank you, Debian team! Regards.