Comment # 5 on bug 1213879 from Dmitriy Markov

(In reply to Michal Suchanek from comment #4)
> IBM recommends disabling TPM and/or secure boot support when OS cannot be
> booted due to insufficient memory
> 
> https://www.ibm.com/support/pages/system-boot-ends-grub-out-memory-oom

We do not use VTPM or secureboot, we have it all turned off. Also in your link
it says that this only applies to Power10. In this discussion Power 8 and Power
9.

If this helps somehow, the update from Leap 15.4 to Leap 15.5 works correctly.
After updating to 15.5 the system boots correctly. In my humble opinion, the
problem is with the images. If I can help you with anything, test something,
please contact me I have a lot of different hardware IBM Power7-9