After a boot entry has been selected in GRUB2, for a short time (1-2 sec) another screen is displayed which shows:
Loading initial ramdisk ...
I found out how to suppress this output (by setting the variable quiet_boot in /etc/grub.d/proxifiedScripts/linux to "1"), but the splash screen with Debian logo still appears.
Is there a way to completely prevent this screen from being shown, or at least replace the background image with a custom one?