Had a little time to do some testing.
Real hardware: Lenovo Thinkpad X260
Live session was OK. Just out of curiosity - is there some reason to include Marble into a minimal test ISO?
Tried also an installation. Installation went OK to the end.
However - booting installed KaOS resulted to:
ERROR: Root device mounted successfully, but /sbin/init does not exist.
Bailing out, you are on your own. Good luck.
sh: can't access tty: job control turned off
[rootfs ]# _
Unfortunately at that moment a quick job arrived and as it is my job laptop, I had to restore my previous distribution.
My GPT partitions were: /dev/sda1 0,25G FAT32 /boot; /dev/sda2 16G btrfs /; /dev/sda3 223G btrfs /home.
/boot and / were formatted during installation and I noticed that root was installed into a subvolume and /sbin/init was there for sure.
Installation log: kaosinstall.zip
If I try again, what to check? The system seems to be there, just some incorrect configuration file? fstab content?