`quiet splash` breaks 20.04.1 server image boot process, but not desktop?

[Loopend]

Hi everyone!

On a fresh 20.04.1 Server installation (no additional packages installed, absolute installer-default minimum set), just adding `quiet splash` to the GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub (which is empty by default), breaks the boot process. Splash is shown and hangs there forever. No console login possible. Adding `nomodeset`has no effect. Same thing on an Intel NUC w/ UEFI and within a Parallels VM.

When using the minimal set of of the corresponding Desktop image on the same hardware, `quiet splash` is the default cmdline and splash works fine.

There are several questions I can't find an answer yet:
 1. What are the differences here?? Shouldn't be a driver issue as only Kernel drivers are used, no proprietary sets. And AFAIK Ubuntu uses the same kernel config for desktop and sever since 12.04 or something.. Any hints which configurations to check for differences?
 2. Tips on how to debug this? As the issue only occurs with `quiet splash` set, I'm not able to see any logs from boot. I guess I could mount the partition with another system after a failed start and inspect log files, but is there a way that doesn't involve a second (or live) system?

Thanks!