Comment 8 for bug 1806961

Is there a particular reason for using LightDM instead of GDM?
I am asking this because I was looking at your previous comment:
'So adding light-locker as a dependency will not work, and I think that
if the lightdm developers are not willing to fix the issue, we should just
remove the package from future releases of ubuntu.'

And it looks like you want an 'one solution fits all' kind of environment.
If this is what you are looking for, you should install a DE (desktop environment,
such as Gnome or KDE) an stick with it.
If you want to customize/change components or even not depend on a DE, then you need
to understand that each package has a specific purpose and that you will have to search
for optional dependencies to achieve what you want.
We cannot add light-locker as a dependency to LightDM because it is not true, you
could install any other alternative screenlocker, not necessarily light-locker.
The more you want to make things your way, the more you need to know and search.

I hope I answered your doubt on why this not a problem of LightDM.

Regarding the problems you are facing with light-locker I think it is misconfiguration
and I will help you on this, it might turn out to be a real problem that we will need
to report.