Display output with rootless X11 only works after X11 has been run once as root

[hacker1024]

It appears that, on an Orin NX at least, no display outputs are detected when running X11 as a non-root user until it has been run as root at least once. This explains why GDM does not seem to work: It is the only major rootless display manager.

X11 log without root (HDMI not working):

(II) LoadModule: "glxserver_nvidia"
(II) Loading /nix/store/hyrfhydisp47a77sqvip4l29hnvd7jzn-nvidia-l>
(II) Module glxserver_nvidia: vendor="NVIDIA Corporation"
        compiled for 1.6.99.901, module version = 1.0.0
        Module class: X.Org Server Extension
(II) NVIDIA GLX Module  35.3.1  Release Build  (bugfix_main)  (bu>
(II) NVIDIA: The X server supports PRIME Render Offload.
(WW) NVIDIA: No DRM device: No direct render devices found.
(II) NVIDIA(0): NVIDIA GPU Orin (nvgpu) (GA10B) at SoC (GPU-0)
(--) NVIDIA(0): Memory: 15747664 kBytes
(--) NVIDIA(0): VideoBIOS:
(II) NVIDIA(0): Validated MetaModes:
(II) NVIDIA(0):     "NULL"
(II) NVIDIA(0): Virtual screen size determined to be 640 x 480
(WW) NVIDIA(0): Unable to get display device for DPI computation.
(==) NVIDIA(0): DPI set to (75, 75); computed from built-in defau>
(II) NVIDIA: Reserving 24576.00 MB of virtual memory for indirect>
(II) NVIDIA:     access.
(WW) NVIDIA(GPU-0): Failed to enter interactive mode.
(EE) NVIDIA(0): Failed to allocate NVIDIA Error Handler
(II) NVIDIA(0): ACPI: failed to connect to the ACPI event daemon;>
(II) NVIDIA(0):     may not be running or the "AcpidSocketPath" X
(II) NVIDIA(0):     configuration option may not be set correctly>
(II) NVIDIA(0):     ACPI event daemon is available, the NVIDIA X >
(II) NVIDIA(0):     try to use it to receive ACPI event notificat>
(II) NVIDIA(0):     details, please see the "ConnectToAcpid" and
(II) NVIDIA(0):     "AcpidSocketPath" X configuration options in >
(II) NVIDIA(0):     Config Options in the README.
(II) NVIDIA(0): Setting mode "NULL"

X11 log with root (HDMI working):

(II) LoadModule: "glxserver_nvidia"
(II) Loading /nix/store/hyrfhydisp47a77sqvip4l29hnvd7jzn-nvidia-l4t-3d-core-35.3.1-20230319081403/lib/xorg/modules/extensions/libglxserver_nvidia.so
(II) Module glxserver_nvidia: vendor="NVIDIA Corporation"
	compiled for 1.6.99.901, module version = 1.0.0
	Module class: X.Org Server Extension
(II) NVIDIA GLX Module  35.3.1  Release Build  (bugfix_main)  (buildbrain@mobile-u64-6289-d7000)  Sun Mar 19 08:02:08 PDT 2023
(II) NVIDIA: The X server supports PRIME Render Offload.
(--) NVIDIA(0): Valid display device(s) on GPU-0 at SoC
(--) NVIDIA(0):     DFP-0
(WW) NVIDIA: No DRM device: No direct render devices found.
(II) NVIDIA(0): NVIDIA GPU Orin (nvgpu) (GA10B) at SoC (GPU-0)
(--) NVIDIA(0): Memory: 15747680 kBytes
(--) NVIDIA(0): VideoBIOS:
(--) NVIDIA(GPU-0): Acer EB321HQ A (DFP-0): connected
(--) NVIDIA(GPU-0): Acer EB321HQ A (DFP-0): Internal TMDS
(--) NVIDIA(GPU-0): Acer EB321HQ A (DFP-0): 600.0 MHz maximum pixel clock
(--) NVIDIA(GPU-0):
(==) NVIDIA(0):
(==) NVIDIA(0): No modes were requested; the default mode "nvidia-auto-select"
(==) NVIDIA(0):     will be used as the requested mode.
(==) NVIDIA(0):
(II) NVIDIA(0): Validated MetaModes:
(II) NVIDIA(0):     "DFP-0:nvidia-auto-select"
(II) NVIDIA(0): Virtual screen size determined to be 1920 x 1080
(--) NVIDIA(0): DPI set to (69, 70); computed from "UseEdidDpi" X config
(--) NVIDIA(0):     option
(II) NVIDIA: Reserving 24576.00 MB of virtual memory for indirect memory
(II) NVIDIA:     access.
(EE) NVIDIA(0): Failed to allocate NVIDIA Error Handler
(II) NVIDIA(0): ACPI: failed to connect to the ACPI event daemon; the daemon
(II) NVIDIA(0):     may not be running or the "AcpidSocketPath" X
(II) NVIDIA(0):     configuration option may not be set correctly.  When the
(II) NVIDIA(0):     ACPI event daemon is available, the NVIDIA X driver will
(II) NVIDIA(0):     try to use it to receive ACPI event notifications.  For
(II) NVIDIA(0):     details, please see the "ConnectToAcpid" and
(II) NVIDIA(0):     "AcpidSocketPath" X configuration options in Appendix B: X
(II) NVIDIA(0):     Config Options in the README.
(II) NVIDIA(0): Setting mode "DFP-0:nvidia-auto-select"

X11 log without root after starting once as root (HDMI working):

(II) LoadModule: "glxserver_nvidia"
(II) Loading /nix/store/hyrfhydisp47a77sqvip4l29hnvd7jzn-nvidia-l4t-3d-core-35.3.1-20230319081403/lib/xorg/modules/extensions/libglxserver_nvidia.so
(II) Module glxserver_nvidia: vendor="NVIDIA Corporation"
        compiled for 1.6.99.901, module version = 1.0.0
        Module class: X.Org Server Extension
(II) NVIDIA GLX Module  35.3.1  Release Build  (bugfix_main)  (buildbrain@mobile-u64-6289-d7000)  Sun Mar 19 08:02:08 PDT 2023
(II) NVIDIA: The X server supports PRIME Render Offload.
(--) NVIDIA(0): Valid display device(s) on GPU-0 at SoC
(--) NVIDIA(0):     DFP-0
(WW) NVIDIA: No DRM device: No direct render devices found.
(II) NVIDIA(0): NVIDIA GPU Orin (nvgpu) (GA10B) at SoC (GPU-0)
(--) NVIDIA(0): Memory: 15747664 kBytes
(--) NVIDIA(0): VideoBIOS:
(--) NVIDIA(GPU-0): Acer EB321HQ A (DFP-0): connected
(--) NVIDIA(GPU-0): Acer EB321HQ A (DFP-0): Internal TMDS
(--) NVIDIA(GPU-0): Acer EB321HQ A (DFP-0): 600.0 MHz maximum pixel clock
(--) NVIDIA(GPU-0):
(==) NVIDIA(0):
(==) NVIDIA(0): No modes were requested; the default mode "nvidia-auto-select"
(==) NVIDIA(0):     will be used as the requested mode.
(==) NVIDIA(0):
(II) NVIDIA(0): Validated MetaModes:
(II) NVIDIA(0):     "DFP-0:nvidia-auto-select"
(II) NVIDIA(0): Virtual screen size determined to be 1920 x 1080
(--) NVIDIA(0): DPI set to (69, 70); computed from "UseEdidDpi" Xconfig
(--) NVIDIA(0):     option
(II) NVIDIA: Reserving 24576.00 MB of virtual memory for indirectmemory
(II) NVIDIA:     access.
(WW) NVIDIA(GPU-0): Failed to enter interactive mode.
(EE) NVIDIA(0): Failed to allocate NVIDIA Error Handler
(II) NVIDIA(0): ACPI: failed to connect to the ACPI event daemon;the daemon
(II) NVIDIA(0):     may not be running or the "AcpidSocketPath" X
(II) NVIDIA(0):     configuration option may not be set correctly.  When the
(II) NVIDIA(0):     ACPI event daemon is available, the NVIDIA X driver will
(II) NVIDIA(0):     try to use it to receive ACPI event notifications.  For
(II) NVIDIA(0):     details, please see the "ConnectToAcpid" and
(II) NVIDIA(0):     "AcpidSocketPath" X configuration options in Appendix B: X
(II) NVIDIA(0):     Config Options in the README.
(II) NVIDIA(0): Setting mode "DFP-0:nvidia-auto-select"