Sorry, I don’t know why I googled around and thought “Poudriere” was the one.

I was thinking of Bastille, which is for managing jails

Ah! No, I haven't used Bastille. I didn't want to rely on fancy wrappers that might go away or change their behavior, so I wrote a shell script that orchestrates some shell tools and ZFS into creating a jail, and that in turn is consumed from Ansible. It doesn't have all the bells and whistles, but it's guaranteed to still be there tomorrow - and that was one of my goals, getting away from all the churn that came from the Linux / Docker ecosystem and finally settle on something!