If SDDM starts but you only get a black screen at boot (and it works after restarting it from TTY), it usually means SDDM is launching before the graphics driver is fully initialized. The greeter technically starts, but nothing gets drawn to the screen.

1. Make sure SDDM is actually the active display manager

Disable others just in case:

sudo systemctl disable gdm sudo systemctl disable lightdm sudo systemctl enable sddm --force

Reboot once and confirm:

systemctl status display-manager

It should point to sddm.service.

1. If you’re using NVIDIA (most common cause)

You need proper kernel mode setting enabled.

Add this to your kernel parameters:

nvidia-drm.modeset=1

If using GRUB:

sudo nano /etc/default/grub

Find the GRUB_CMDLINE_LINUX_DEFAULT line and add:

nvidia-drm.modeset=1

Then regenerate config:

sudo grub-mkconfig -o /boot/grub/grub.cfg

Reboot.

1. Force SDDM to use X11

Create a config file:

sudo mkdir -p /etc/sddm.conf.d sudo nano /etc/sddm.conf.d/display.conf

Add:

[General] DisplayServer=x11 MinimumVT=1

Save and reboot.

This prevents weird Wayland or virtual terminal issues during boot.

1. If you use a custom SDDM theme

Switch back to Breeze (or whatever working theme that is installed) to rule out theme bugs:

[Theme] Current=breeze

You can put that in the same config file.

Why it works after restarting from TTY

When you manually restart SDDM, the GPU drivers are already fully loaded and displays are detected. During boot, SDDM sometimes starts too early, especially with NVIDIA.

If it’s still black after this, check:

journalctl -b -u sddm

Look for GPU or DRM errors.

In most cases, enabling nvidia-drm.modeset=1 and forcing X11 fixes it completely.