Comment 8 for bug 1973628

So I'm getting further than before, using for example:
$ sudo autopkgtest-buildvm-ubuntu-cloud -r jammy -v --cloud-image-url http://cloud-images.ubuntu.com/daily/server -s 15G -a ppc64el --ram-size=8192

But the image preparation still fails (I think this is more a follow-on error):

...
Tue, 23 Aug 2022 16:29:10 +0000. Up 524.83 seconds.
[ 527.034556] cloud-init[1270]: 2022-08-23 16:29:12,713 - util.py[WARNING]: Running module ssh-authkey-fingerprints (<module 'cloudinit.config.cc_ssh_authkey_fingerprints' from '/usr/lib/python3/dist-packages/cloudinit/config/cc_ssh_authkey_fingerprints.py'>) failed

[ 527.260692] cloud-init[1270]: Cloud-init v. 22.2-0ubuntu1~22.04.3 finished at Tue, 23 Aug 2022 16:29:12 +0000. Datasource DataSourceNoCloud [seed=/dev/vdb][dsmode=net]. Up 527.18 seconds
[FAILED] Failed to start Execute cloud user/final scripts.
See 'systemctl status cloud-final.service' for details.
[ OK ] Reached target Cloud-init target.
timed out on cloud-init
qemu-system-ppc64le: terminating on signal 15 from pid 3614 (/usr/bin/python3)

or in a different attempt (where I used '--ram-size=4096'):
...
[ 3532.036566] cloud-init[1393]: Failed to get unit file state for apt-daily-upgrade.timer: Failed to activate service 'org.freedesktop.systemd1': timed out (service_start_timeout=25000ms)
[ 3557.272658] systemd-journald[332]: Failed to send WATCHDOG=1 notification message: Transport endpoint is not connected
[ 3557.277579] cloud-init[1393]: Failed to retrieve unit state: Failed to activate service 'org.freedesktop.systemd1': timed out (service_start_timeout=25000ms)
[ 3557.286250] cloud-init[1393]: apt-daily-upgrade.timer is a disabled or a static unit not running, not starting it.
timed out on cloud-init
qemu-system-ppc64le: terminating on signal 15 from pid 3452 (/usr/bin/python3)