Comment 9 for bug 1970081

I recently realized slick-greeter was no more used, since "Arctica Greeter" was used instead. So I adopted the procedure pointed here: https://ubuntu-mate.community/t/how-to-change-lockscreen-and-login-wallpaper-with-arctica-greeter/24242/2 . So I could finally see the background I previously set in vain with "lightdm-settings". I cannot tell why the background in the password input boxes is white, though.