I’m on Debian with XFCE I’ve already tried modifying /etc/default/grub and /etc/lightdm/lightdm-gtk-greeter.conf The first resulted in nothing (I actually have grub timeout set to 0, so I’m not sure if I only need changing grub’s config), the bootsplash was still default The second resulted in black login bg
there’s likely at least 3: one for the bootloader; one for the display manager; and one for your screen wallpaper.
it’s the same w windows