Comment 65 for bug 1970069

The blanking from GRUB_TIMEOUT>0 will be made much worse by CONFIG_FB_EFI=n because usually in Ubuntu it's the efifb that restores the logo after Grub has wiped it. I think not having CONFIG_FB_EFI at the same time as using GRUB_TIMEOUT>0 explains your previous "really long time of a black screen".

I can tell you've restored GRUB_TIMEOUT=0 in the video and the one remaining screen blank at Plymouth's startup might be bug 1836858. But either way it's not this bug. Related bugs can be found at https://bugs.launchpad.net/ubuntu/+bugs?field.tag=flickerfreeboot