Lenovo screen backlight can not set with brightness function Fn keys

Being aware of that this is partially a known issue, since each is individual and different, the problem is as following: On my Lenovo Laptop with Linux Mint the backlight cannot be set using Fn+F6/F7. These keys are not detected at all, neither by xev nor by acpi_listen. However other key combinations like Fn+F3 for volume up is detected by both commands. So it is a more low-level issue, I am afraid. On the other hand, this works well: - echo 10000 | sudo tee /sys/class/backlight/intel_backlight/brightness and as well - with the GUI slider in mate-power-preferences works perfectly. - xdotool key 232 or xdotool key XF86MonBrightnessDown More detailed: - I tried many boot combinations (yes I updated GRUB and did reboot, as described in this troubleshooting wiki.ubuntu.com Debugging/Backlight ) - I tried adding files in /usr/share/X11/xorg.conf.d/ as recommended (80-backlight.conf using both "Backlight" "ideapad" and "intel_backlight", or 20-intel.conf) uname -a yields: Linux Lenovo-V14-G2-ITL 5.8.0-53-generic #60~20.04.1-Ubuntu SMP Thu May 6 09:52:46 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux These are the available backlights (which can be written using cat) $ ls /sys/class/backlight/ ideapad intel_backlight This is my current configuration $ cat /proc/cmdline BOOT_IMAGE=/vmlinuz-5.8.0-53-generic root=/dev/mapper/vgmint-root ro pcie_aspm=force acpi_osi=Linux acpi_backlight=vendor quiet splash I tried these (as well individually and with many combinations, only visible effect is that the output of ls /sys/class/backlight/ is changing) GRUB_CMDLINE_LINUX="pcie_aspm=force acpi_osi=linux acpi_backlight=vendor video.use_native_backlight=1"