aus Kernel-Parameter Dokumentation
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acpi_backlight= [HW,ACPI] { vendor | video | native | none } If set to vendor, prefer vendor-specific driver (e.g. thinkpad_acpi, sony_acpi, etc.) instead of the ACPI video.ko driver. If set to video, use the ACPI video.ko driver. If set to native, use the device's native backlight mode. If set to none, disable the ACPI backlight interface.…
acpi_backlight=native
Wäre ggf. auch ein Versuch wert.