After I submitted my initial post I was pointed to similar ones. As a result I re-formatted the bigger disk for XFS with d_type functionality enabled. And we put:
{
"storage-driver": "overlay2",
"storage-opts": [
"overlay2.override_kernel_check=true"
]
}
in /etc/docker/daemon.json from https://docs.docker.com/engine/userguide/storagedriver/overlayfs-driver/#configure-docker-with-the-overlay-or-overlay2-storage-driver
This allowed us to install the container with the base discourse. After we added the socket template we got an error related to Nginx starting up in the container but quickly fixed that. We then restored the Discourse backup and now know how to resurrect the site in production. Thanks for your help.