some details for the upgrade are missing

Please add following steps like:

- if you have a external Issuer types you need to uninstall this external issuer before you delete cluster operator.

- you have to make sure that you have a backup of all existing issuer, clusterissuer, and certificates. Or at least they are recreated by some gitops features.
you can get a list of the existing objects by:
$ oc get issuers.cert-manager.io -A
NAMESPACE      NAME                               READY   AGE
cert-manager   letsencrypt-issuer                 True    19h
$ oc get clusterissuers.cert-manager.io -A
NAME                        READY   AGE
letsencrypt-clusterissuer   True    19h
$ oc get certificates.cert-manager.io -A
NAMESPACE           NAME                                  READY   SECRET                                AGE
kafka               my-cluster-certificate                True    my-cluster-certificate                18h
...

Additioninal question:
what's about the certmanagers.config.openshift.io, shouldn't it be deleted as well.