duh. tmpfs.
So, it should be obvious that by mounting the installation system through BootX, and using “df” to show what’s mounted, that the file system & changes I made wouldn’t be remembered by the tmpfs file system. So upon reboot into Linux I got kernel panic- couldn’t find the reoot device. Fortunately the changes I’d made were still there.
I tried debootstrap with a couple other distro CDs I had around and got the same errors with chroot.
I’m going to combine the debootstrap command line approach in combination with a Debian woody ppc distro install, hoping that the boot floopies will be better suited to chroot into a debootstrapped new Debian installation.