Very well said. Thank you very much for your help. I wouldn’t have known to check the ownership issues or if GDM were properly running Wayland were it not for your help. I’ll reach out to the GNOME devs on the relevant repositories and see if they might be able to point me in the right direction. Thank you for your time and expertise.

Yes. Here’s the contents I currently have in /var/lib/gdm/.config/monitors.xml:

<monitors version="2">
  <configuration>
    <layoutmode>physical</layoutmode>
    <logicalmonitor>
      <x>0</x>
      <y>0</y>
      <scale>1</scale>
      <primary>yes</primary>
      <monitor>
        <monitorspec>
          <connector>DP-1</connector>
          <vendor>SAM</vendor>
          <product>Odyssey G93SC</product>
          <serial>HNTW700164</serial>
        </monitorspec>
        <mode>
          <width>5120</width>
          <height>1440</height>
          <rate>239.997</rate>
        </mode>
        <colormode>bt2100</colormode>
      </monitor>
    </logicalmonitor>
    <disabled>
      <monitorspec>
        <connector>HDMI-1</connector>
        <vendor>FUN</vendor>
        <product>Evanlak8K V2</product>
        <serial>0x00006410</serial>
      </monitorspec>
    </disabled>
  </configuration>
</monitors>

The disabled dummy plug is the “Evanlak8K V2” device while my functional monitor is my Samsung Odyssey OLED G9. This config is the same as the one currently running on my GNOME desktop config, but in GDM still defaults to the enabled dummy plug, even with the fixed ownership.

At this point, do you think I should issue a report on GDM’s repository? Maybe the devs there would have more insight

Just checked the ownership of the monitor config, it was gdm:root, so I changed the ownership to gdm:gdm and rebooted. Still facing the same issue.

Didn’t see any error messages in the logs about not being able to load wayland, but just to confirm, I ran loginctl show-session {gdm session id} -p Type which returns Type=wayland, so it’s definitely running under wayland. I have an AMD GPU though so I wouldn’t expect there to be any problems there.

Not seeing anything else weird in the logs that are jumping out as strange to me either, so a bit at a loss here. Any other suggestions?