How to overcome 'The field 'loop' is supposed to be a string type' failure during create_ceph_initial_dirs installation task?

Issue

Ceph installation ends with the following failure:

$ ansible-playbook site.yml 

2020-11-18 16:16:17,087 p=20776 u=admin |  TASK [ceph-config : include create_ceph_initial_dirs.yml]
task path: /usr/share/ceph-ansible/roles/ceph-config/tasks/main.yml:2 ********************************************************************************************
2020-11-18 16:16:17,088 p=20776 u=admin |  Wednesday 18 November 2020  16:16:17 +0100 (0:00:00.073)       0:02:43.380 ****
2020-11-18 16:16:17,153 p=20776 u=admin |  fatal: [ceph-mon1]: FAILED! => {"failed": true, "reason": "The field 'loop' is supposed to be a string type, however the incoming data structure is a <class 'ansible.parsing.yaml.objects.AnsibleSequence'>\n\nThe error appears to have been in '/usr/share/ceph-ansible/roles/ceph-config/tasks/create_ceph_initial_dirs.yml': line 2, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n---\n- name: create ceph initial directories\n  ^ here\n"}
2020-11-18 16:16:17,153 p=20776 u=admin |  fatal: [ceph-mon2]: FAILED! => {"failed": true, "reason": "The field 'loop' is supposed to be a string type, however the incoming data structure is a <class 'ansible.parsing.yaml.objects.AnsibleSequence'>\n\nThe error appears to have been in '/usr/share/ceph-ansible/roles/ceph-config/tasks/create_ceph_initial_dirs.yml': line 2, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n---\n- name: create ceph initial directories\n  ^ here\n"}
2020-11-18 16:16:17,154 p=20776 u=admin |  fatal: [ceph-mon3]: FAILED! => {"failed": true, "reason": "The field 'loop' is supposed to be a string type, however the incoming data structure is a <class 'ansible.parsing.yaml.objects.AnsibleSequence'>\n\nThe error appears to have been in '/usr/share/ceph-ansible/roles/ceph-config/tasks/create_ceph_initial_dirs.yml': line 2, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n---\n- name: create ceph initial directories\n  ^ here\n"}
2020-11-18 16:16:17,155 p=20776 u=admin |  PLAY RECAP *******************************************************************************************************************************************
2020-11-18 16:16:17,155 p=20776 u=admin |  ceph-mon1                  : ok=77   changed=4    unreachable=0    failed=1
2020-11-18 16:16:17,155 p=20776 u=admin |  ceph-mon2                  : ok=71   changed=4    unreachable=0    failed=1
2020-11-18 16:16:17,155 p=20776 u=admin |  ceph-mon3                  : ok=71   changed=4    unreachable=0    failed=1