As the Debian installer does not support to install on ZFS (due to potential legal incompatibilities between their licenses), this needs to be done manually (and as usual due to non-free firmware, Wifi is not supported out of the box by Debian, so you need tp have an Ethernet cable connection):

I found a good Howto:

• https://openzfs.github.io/openzfs-docs/Getting%20Started/Debian/Debian%20Bookworm%20Root%20on%20ZFS.html

There are minor things to be noted:

1. ashift=12 Some suggest that for SSDs a higher value might be better, e.g., 13. Still need to monitor wearout as ZFS has been reported to kill your SSD after a year.
2. autotrim=on It is often said, that rather a Cron jobs should do this, e.g., weekly.

Note that the above Howto contains also Rescuing using a live CD that might be helpful for rescuing.

I found two further howtos, that are somewhat different, due things in a slightly different order, but are more detailed and explicitly mention implicit steps:

• https://www.dwarmstrong.org/debian-install-zfs/ (e.g. discusses swap partition -- the above first Howto uses a ZFS zvol for this, but but this would not work for hibernate as ZFS is not known during hibernation)
• https://docs.zfsbootmenu.org/en/v2.3.x/guides/debian/bookworm-uefi.html

I followed mainly the first howto with some inspiration from the two others. E.g. I created a standard swap partition. TODO: Enable swap and hibernate.

ZFS enables to do snapshots before and after system updates
(TODO: can this be added to any apt upgrade, incl. unattended upgrades?)

Note: After having selected KDE in tasksel, the system did not get KDE started: the textual boot was stuck at the latest task before KDE would be started (some cups stuff): I did then a apt install firmware-amd-graphics and after a reboot, it worked -- not sure whether a reboot alone would have already solved the problem or not.

For my T14, I also installed the WiFi drivers.