Debian 12 installation on iMac G3

Hi all!

I have several PowerPC based computers. One of them is an iMac G3/500 DV SE
(powermac2,2) with 1 GB RAM and 30 GB hard drive.

I've had it with Ubuntu 14.04 LTS but it's out of support already. It
worked fine from boot perspective, and it was using yaboot.

I wanted to install Debian 12, now that I know that the architecture is
being maintained.
I downloaded and installed it from this image:
https://cdimage.debian.org/cdimage/ports/snapshots/2024-02-25/debian-12.0.0-powerpc-NETINST-1.iso
.

The disk layout for this installation was:

Device / Size / Type / Mount point / Bootable
-------------------------------------------------------
/dev/sda13 128MB HFS /boot/grub yes
/dev/sda14 11GB ext4 / no
/dev/sda15 512MB swap no

However, when it comes the time to install grub, the system hangs at 16%
progress of that stage.
I opened a console and checked. The process hung was grub-ieee1275

The system log (Alt+F4) showed a dump of a killed process.

I was able to kill that and finish the installation (users etcetera).
I booted in rescue mode. Then mounted and verified that /boot/grub was r/w.
Then tried to complete the installation, to no avail. The error message
this time:

Installing for powerpc-ieee1275 platform . Errors were encountered while
processing grub-ieee1275

Any hint of what I'm missing or doing wrong?
Any hint will be very much appreciated.

-- 
Regards,

     Manuel Molina Cuberos