Looking deeper, I noticed that the "default" theme directory is actually a link to "webkit", so there is only one theme installed, and one file ("/usr/share/lightdm-webkit/themes/webkit/index.html") to look at.
Looking deeper, I noticed that the "default" theme directory is actually a link to "webkit", so there is only one theme installed, and one file ("/usr/ share/lightdm- webkit/ themes/ webkit/ index.html" ) to look at.