SOLVED: Problems booting Linux on Intel NUC 12 Enthusiast A770m

[jketreno]

I have an Intel NUC 12 Enthusiast which has an Intel Arc A770m. When booting with HDMI connected to a monitor, I was faced with the A770M (PCI device ID 8086:5960) not consistently enumerating on the PCI bus.

Sometimes it would be there:

$ ls /dev/dri/render*
/dev/dri/renderD128  /dev/dri/renderD129
$ lspci -nnn | grep 5960 
03:00.0 VGA compatible controller [0300]: Intel Corporation Device [8086:5690] (rev 08)

Sometimes it wouldn't:

$ ls /dev/dri/render*
/dev/dri/renderD128 
$ lspci -nnn | grep 5960

Another user suggested trying to disable the NUC's BIOS setting for "Native ACPI OS PCIe Support" (F2 on boot to BIOS, go to Power, Secondary Power Settings, and turn off "Native ACPI OS PCIe Support", then Save and Exit (F10).) I gave it a shot, and now the device appears on the PCI bus every boot.

I wanted to share here in case others encounter the same problem.