I have successfully compiled on G4 powerpc libguestfs ( last stable version 1.26.0 ) and supermin 5.1.7 but

supermin doesn't recognise a suitable kernel ( vmlinuz*) to build the appliance, looking on the kernel.ml code (language that I never have seen) I have see that it check only i386 and arm architecture, in any case look like it search a vmlinuz* with host_cpu, in case of powerpc look like it search vmlinuz*powerpc*

In my /boot I have only 2 kernel with powerpc inside ( vmlinux-3.11.0-6-powerpc-smp) and the 3.13.9 with out (vmlinux-3.13.9kvmth) and with vmliux not vmlinuz

I have tried to make symlink of my vmlinux with vmlinuz*powerpc* but the error is the same:
supermin -v -v -v --build --format ext2 supermin.d -o appliance.d

supermin: failed to find a suitable kernel.

I looked for kernels in /boot and modules in /lib/modules.

My impression is that supermin5 doesn't work properly building aplliance with powerpc architecture.

Thanks for your time