PPC Mac partition oddity

I have an old Powerbook and wanted to mount a USB drive I formatted with it on a Linux box. The Linux computer had a custom kernel with mac partition support (CONFIG_MAC_PARTITION). Oddly, the kernel didn't recognize the partitions on the drive.

Unfortunately the Powerbook's display is broken and I can't confirm it uses open firmware, but all sources I found say it does.

So I thought EFI GUID Partition support was not necessary, but it turns out that PPC macs can use that partition type as well, so CONFIG_EFI_PARTITION is necessary.