Comment # 9 on bug 1185601 from Wolfgang Frisch

I encountered the same problem on a Dell Precision 5530 with Intel graphics.
Linux 5.11.16 is fine. Blank screen with 5.12. dmesg excerpt:

>[  115.111238] ACPI BIOS Error (bug): Could not resolve symbol [\_SB.PCI0.PEG0.PEGP.BRT6.LCD], AE_NOT_FOUND (20210105/psargs-330)
>[  115.111265] ACPI Error: Aborting method \_SB.PCI0.PEG0.PEGP.BRT6 due to previous error (AE_NOT_FOUND) (20210105/psparse-529)
>[  115.111550] ACPI Error: Aborting method \EV5 due to previous error (AE_NOT_FOUND) (20210105/psparse-529)
>[  115.111722] ACPI Error: Aborting method \SMEE due to previous error (AE_NOT_FOUND) (20210105/psparse-529)
>[  115.111883] ACPI Error: Aborting method \SMIE due to previous error (AE_NOT_FOUND) (20210105/psparse-529)
>[  115.112042] ACPI Error: Aborting method \NEVT due to previous error (AE_NOT_FOUND) (20210105/psparse-529)
>[  115.112201] ACPI Error: Aborting method \_SB.PCI0.LPCB.ECDV._Q66 due to previous error (AE_NOT_FOUND) (20210105/psparse-529)