A simple dark theme for sddm
$ git clone https://github.com/michaelgilch/dark-arch-sddm
$ cd dark-arch-sddm
$ ./install.sh #Requires sudo authentication while installing
Then, apply the theme in /etc/sddm.conf.d/default.conf.
Did you know? In install.sh you can easily select the logo you prefer. Isn't it in the list? Open an issue here on GitHub specifying the distro name and a url to the logo you want.
