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systemd: intercepting poweroff, shutdown, reboot and alert us we still have KVM QEMU guest(s) running

I want to interrupt a poweroff or reboot if KVM/QEMU Guests are still running.
It should work regardless whether shutdown/reboot is requested from XFCE, or from terminal. I already have a script that checks virsh list --all for ‘running’ and sounds an alert every ten seconds until no longer true. I’m just trying to insert it in the shutdown process, creating a delay so I may shutdown guests before shutdown continues.

I occasionally make the mistake of shutting down my system with KVM/QEMU guest(s) still running, resulting in long delay, and forced shutdown of the guest(s).
This is not a server. It’s my notebook, running Debian 11 xfce.
I understand guests that speak ACPI can be told to shutdown automatically. If it was a short static list of guests I might try to ensure ACPI works on all guests, but it’s not.

I found this https://www.psdn.io/posts/systemd-shutdown-unit/
Wow, besides being a lot of work, it seems rather fragile.
Is there a better way?