Generate Scarthgap genericx86-64 machine booting pcbios

Hi community,

I've looked around how to get the example meta-yocto-bsp running on genericx86-64. By creating the default image it spits out the efi version which boots up quick and fine. In my target application I have to support the non efi world too. So I tried to switch by feeding the appended wks file to create the pcbios version:

part /boot --source bootimg-pcbios --ondisk sda --label msdos --active --align 1024 --use-uuid
part / --source rootfs --ondisk sda --fstype=ext4 --label platform --align 1024 --use-uuid
part swap --ondisk sda --size 44 --label swap1 --fstype=swap
bootloader --ptable gpt --timeout=5 --append="rootfstype=ext4 console=tty0"

Problem is: it stops by Kernel panic - not syncing: Invalid configuration from end user prevents continuing
Hardware name: Deault string Default string/Default string, BIOS 5.13 01/18/2024

Unfortunately there is not more I can read.

Can anyone explain me where I missed a step?

Regards,

Sebastian