📝 post-install: add steps for lightdm greeter

docs/Linux_Post_Install.md

@@ -110,8 +110,14 @@ See more @ https://github.com/manilarome/lightdm-webkit2-theme-glorious
 
 ```bash
 # Set default lightdm greeter to lightdm-webkit2-greeter
-sudo sed -i 's/^\(#?greeter\)-session\s*=\s*\(.*\)/greeter-session = lightdm-webkit2-greeter #\1/ #\2g' /etc/lightdm/lightdm.conf
+sudo vim /etc/lightdm/lightdm.conf
+```
+```conf
+[Seat:*]
 
+greeter-session=lightdm-webkit2-greeter
+```
+```bash
 # Set default lightdm-webkit2-greeter theme to Glorious
 sudo sed -i 's/^webkit_theme\s*=\s*\(.*\)/webkit_theme = glorious #\1/g' /etc/lightdm/lightdm-webkit2-greeter.conf
 sudo sed -i 's/^debug_mode\s*=\s*\(.*\)/debug_mode = true #\1/g' /etc/lightdm/lightdm-webkit2-greeter.conf