Asus Zenbook Duo UX8406MA Regression - Display Blank

The Asus Zenbook Duo UX8406MA is an Intel Metor Lake laptop with two builtin displays. After upgrading the kernel on these systems to the kernel 6.9 tree or later (latest known working version 6.8.12), the secondary display remains blank regardless of any display configuration changes made to the running system.

Another user (@hacker1024 on the NixOS Discourse) has been trying to improve functionality with this machine, and bisected the secondary display problem down to 480e035f ("Merge tag 'drm-next-2024-03-13' of https://gitlab.freedesktop.org/drm/kernel").

A number of errors are logged while running the system in this nonfunctional state; this is from a 6.9.5 kernel; a full debug output dump reproducing the issue is also attached to give these messages context zenbook-6.9-journalctl-debug.txt Note that there are two other external DP displays connected during this boot, but eDP-2 is the display that is the focus of this issue which remains blank.

kernel: i915 0000:00:02.0: [ENCODER:244:DDI B/PHY B] PPS 0 panel power already on
kernel: i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device
kernel: i915 0000:00:02.0: drm_WARN_ON(intel_dp->pps.vdd_wakeref)
kernel: i915 0000:00:02.0: Use count on domain AUX_B is already zero
kernel: i915 0000:00:02.0: Use count on power well AUX_B is already zero
kernel: i915 0000:00:02.0: [drm] [transcoder A] PSR aux error
kernel: i915 0000:00:02.0: [drm] [transcoder A] PSR aux error
kernel: i915 0000:00:02.0: drm_WARN_ON(intel_dp->pps.vdd_wakeref)
kernel: i915 0000:00:02.0: drm_WARN_ON(power_domains->domain_use_count[domain] != 1)
(repeat 10 times)
kernel: i915 0000:00:02.0: Use count on domain AUX_B is already zero
kernel: i915 0000:00:02.0: Use count on power well AUX_B is already zero
kernel: i915 0000:00:02.0: drm_WARN_ON(power_domains->domain_use_count[domain] != 1)
(repeat 22 times)
kernel: i915 0000:00:02.0: Use count on domain AUX_B is already zero
kernel: i915 0000:00:02.0: [drm] [transcoder B] PSR aux error
kernel: i915 0000:00:02.0: [drm] [transcoder B] PSR aux error
(same messages repeat occasionally)

PCI device information:

lspci -vnn -d :\*:0300
0000:00:02.0 VGA compatible controller [0300]: Intel Corporation Meteor Lake-P [Intel Arc Graphics] [8086:7d55] (rev 08) (prog-if 00 [VGA controller])
        DeviceName: VGA
        Subsystem: ASUSTeK Computer Inc. Device [1043:1c43]
        Flags: bus master, fast devsel, latency 0, IRQ 129, IOMMU group 0
        Memory at 5010000000 (64-bit, prefetchable) [size=16M]
        Memory at 4000000000 (64-bit, prefetchable) [size=256M]
        Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
        Capabilities: <access denied>
        Kernel driver in use: i915
        Kernel modules: i915, xe

Motherboard information dmidecode.txt

Handle 0x0000, DMI type 0, 26 bytes
BIOS Information
        Vendor: American Megatrends International, LLC.
        Version: UX8406MA.306
        Release Date: 05/03/2024
        Address: 0xF0000
        Runtime Size: 64 kB
        ROM Size: 32 MB
        Characteristics:
                PCI is supported
                BIOS is upgradeable
                BIOS shadowing is allowed
                Boot from CD is supported
                Selectable boot is supported
                BIOS ROM is socketed
                EDD is supported
                ACPI is supported
                Smart battery is supported
                BIOS boot specification is supported
                Targeted content distribution is supported
                UEFI is supported
        BIOS Revision: 5.32