Just an FYI. I had to restore

/oem/90_custom.yaml

from a

/oem/install/90_custom.yaml.*

on node that no longer allowed login due to the broken

/oem/90_custom.yaml

. I was able to copy over the backup configuration file with booting into initramfs via option recovery in Grub, then mounting the respective partition (for me it was

nvme0n1p2

, a a 50M partition out of 5 or 6 partitions), and issuing the

cp

command.