leap 15.5 on power8

Hello SUSE people,

I tried to install leap 15.5 on a power8 and ran into this: https://www.ibm.com/support/pages/could-not-allocate-memory-rtas-grub-or-yaboot-ppcbe

I followed the instructions there but that only got me a few lines further before the same error kicked in again. I also tried tumbleweed which crashed with a slightly different error. However I guess tumbleweed doesn’t support power8 anymore but leap 15 should as far as I could find out.
So right now that means no SUSE for me. What can i do to get this working?

Thanks in advance for any hints!