machinectl(1) states the following:
systemd-machined.service(8)also interfaces with a variety of other container and VM managers,
systemd-nspawnis just one implementation of it.
What are the other container (and VM) managers that
systemd-machined.service can interface with?
I can surmise that
Docker is not on the list because lightweight containers for the purpose of application sandboxes are excluded.