GDM's greeter requires gnome-session-x11@gnome-login.target (from gnome-shell), which isn't installed on i3-only setups. This caused gnome-session to crash-loop, leaving a blank screen on boot. LightDM works without gnome-shell and is a better fit for i3. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>