Reported issue: the login screen (lightdm) doesn’t start after the first boot from a hard drive, after installing Sparky.
Possible reason: plymouth
To temporary handle with that, edit kernel starts options via GRUB.
Press ‘e’ key to edit it.
Go to the end of the line started with “linux” and delete ‘quiet splash’ options.
Than press “F10” key to boot.
It happens on some machines/some hardware.
Make sure that Sparky is based and fully compatible with Debian ‘testing’, so situations like that sometimes happen.
If you looking for a rock stable operating system – choose Debian ‘stable’.