Cannot disable secondary monitor in SDDM Astronaut theme under Wayland

[EmbedJunk]

I'm trying to configure the SDDM Astronaut theme on a Wayland system (Hyprland) so that the secondary monitor is disabled during the login screen.

What I tried:

Setting DisplayServer=x11 and using /usr/share/sddm/scripts/Xsetup with xrandr --output HDMI-A-2 --off – does not work under Wayland, only works on X11.

Using wlr-randr --output HDMI-A-2 --off in XSetup – the login screen is displayed correctly on the left monitor, but Hyprland crashes immediately after login.

Editing any theme .conf files in /usr/share/sddm/themes/sddm-astronaut-theme/Themes/ – there is no option to disable monitors or set monitor priority.

Trying to find or edit any .json or other configuration files for SDDM (like kwinoutputconfig.json) – does not exist for this theme/setup.

Observed behavior:

On Wayland, the SDDM Astronaut theme greeter runs in a separate wlroots session.

Any attempt to disable or turn off the secondary monitor either has no effect (XSetup/xrandr) or causes the Wayland session (Hyprland) to crash (wlr-randr).

The theme provides no configuration for controlling which monitor the greeter appears on.

Expected behavior:

Ability to disable or hide secondary monitors during the login screen using the Astronaut theme configuration or some supported method.

Preferably, ability to retain the Astronaut theme look while controlling monitor display.

System information:

Arch Linux

Hyprland (Wayland)

SDDM Astronaut theme latest version

Additional context:

This seems to be a limitation of SDDM-Wayland + Astronaut theme: the greeter runs in its own wlroots instance, so monitor configuration outside the greeter session does not reliably apply.

[JohnnyJumper]

it might be that the displays has different name under X11 and Wayland although the ports are the same.

I had similar issue and resolved it like so:

/usr/share/sddm/scripts/Xsetup

#!/bin/sh
# Xsetup - run as root before the login dialog appears

xrandr > /tmp/xrandr-sddm.log

xrandr --output DP-2 --primary --auto \
       --output DP-4 --off \
       --output HDMI-0 --off

xrandr > /tmp/xrandr-sddm.log is what gave me a hint. after log in you can check the file and see the names of the monitors. I found that on Wayland my primary monitor is called DP-3 but on X11 it is DP-2 so changing the config fixed the problem. Although right now I am like a sitting duck waiting for Wayland or X11 to just rename the ports but that is a problem for the future.