Oh, and also, there's a little gotcha: Software Factory version 3.6 (the current supported release) has "zuul-worker" hardcoded as the default user for images. OpenDev has the zuul-worker element [4] which creates the zuul user and sets up SSH key pairs. Software Factory has an equivalent element called zuul-worker-user, which does the same but for a zuul-worker user. Pay attention if the user configured in nodepool.yaml (the default in SF is "zuul-worker") is the user your element has set up the SSH key pairs for. In the next release I believe SF won't hardcode "zuul-worker" anymore, and will use the default from Zuul itself, which is simply "zuul"

[4] https://opendev.org/openstack/project-config/src/branch/master/nodepool/elements/zuul-worker/install.d/60-zuul-worker#L9-L30
[5] https://softwarefactory-project.io/cgit/software-factory/sf-elements/tree/elements/zuul-worker-user/post-install.d/50-zuul-worker-user-authorized_keys#n14