Failures attempting to install in an LDOM

I finally got round to trying to install debian-sparc in an LDOM on my T4
server.

Sadly, this didn't work.

With Debian 12, software installation fails. I see

Jun 10 08:43:02 in-target: The following packages have unmet dependencies:
Jun 10 08:43:03 in-target:  console-setup-linux : Depends:
keyboard-configuration (= 1.220) but 1.227 is installed

along with some unrelated dpkg-deb segfaults. Ignoring that, the bootloader
won't install.

With Debian 10, it appears that software installation succeeds, but again
the bootloader fails to install.

Is there a known-to-work set of instructions available that would get me
closer to a working install?

Thanks,