Hello, browsing the mailing list archive I read that on December 2018 people with a Macintosh G5 was kindly asked to try Fedora and OpenSUSE to see if their GRUB works [1].
I was not member of the list at the time, but now I am. I have a PowerMac G5 late 2005 and if this kind of help/test is still needed I will give it a try. [1] https://lists.debian.org/debian-powerpc/2018/12/msg00010.html Regards F.