Hello Chris, Ludo and Efraim, In my experience, the bootstrap binaries are reproducible on powerpc64le-linux-gnu for a specific GNU Guix System and GNU Guix version and configuration. It's not perfect that the kernel version has to be pinned for reproducibility but it's better than nothing.
The issue with powerpc64le-linux-gnu on GNU Guix core-updates now is that it has been upgraded to Glibc 2.32 and there is other issues due to that. Glibc 2.31 is otherwise working well. I wish we could push changes to build bootstrap binaries to master where there is Glibc 2.31 (and ensure the changes don't affect other architectures) and get this over with. Leo