I have also seen this message in the lightdm log:[+0.06s] WARNING: Error getting user list from org.freedesktop.Accounts: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.Accounts was not provided by any .service files
This went away when I installed accountsservice. I believe that either lightdm itself or maybe the greeter package should depend on accountsservice. Regards, Phil.