I installed deepin on Arch (fresh install) and it just isn't working, I can't log in, when I start the lightdm.service, it just shows blank white screen. I haven't enable the service yet. I was just checking if it worked and its not working.
There might be an issue with the lightdm-deepin-greeter.
Install an alternative greeter, e.g lightdm-gtk-greeter
sudo pacman -S lightdm-gtk-greeter
Then edit /etc/lightdm/lightdm.conf
sudo nano /etc/lightdm/lightdm.conf
Look for the line that is like
greeter-session=lightdm-deepin-greeter or the value could be something else
change it to
ctrl-x, y, [enter]
Stop & start the lightdm.service and see if that works.
systemctl stop lightdm systemctl start lightdm