The ceph_release variable is not being defined, which is why this failure is happening. Could you include your full configuration, playbook, inventory and full log.
I think this upstream PR should address the problem. We really shouldn't be doing version checks in ceph-validate anyway. If you do not run ceph-defaults and pass ceph_stable_release these will never pass anyway in ceph-validate.
Present in https://github.com/ceph/ceph-ansible/releases/tag/v3.2.0beta5
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.