Date: 2025sep3 OS: Raspberry Pi OS Q. Raspberry PI OS: Failed to start lightdm A. This worked for me:

sudo apt remove lightdm sudo apt purge lightdm sudo apt install lightdm sudo raspi-config (Select boot to desktop)

Reboot, then do:

sudo apt install raspberrypi-ui-mods

Summarized from https://forums.raspberrypi.com/viewtopic.php?t=356467