Hello,

According to the following link:
https://www.youtube.com/watch?v=6JhMSKvf6Kw
The "EFI variables are not supported on this system" can be fixed by running:

modprobe efivarfs
mount -t efivarfs efivarfs /sys/firmware/efi/efivars

According to few links I found, the cause is that Knoppinx (in my case) is booting from USB stick.
I think (not sure) this is a BUG.

Thank you,
Zvika