I'm currently using Manjaro budgie, but this 2 DE's are very very similar (at least until now).
That said I had the exact same issue with this last update, IDK exatly what happened... but it seems LightDM got screwed really good.
Firstly my LightDM menu shows that all files that were loads by the greeter (themes and icons) got lost (it seems like this files got deleted somehow).
In addition to that if I run "systemctl status lightdm.service" shows an error also. So, yes, something went really wrong in this last update and I still don't know what exactly went wrong.