In OpenShift 4.17 is supported Logging 5.8 as visible in the "OpenShift Operator Life Cycles" webpage [0]

Then, it should be included documentation for Logging 5.8 in OpenShift 4.17 taking into consideration that starting in OpenShift 4.16 is only supported the ClusterLogging Operator and not the Elasticsearch Operator, then, all the references to Elasticsearch should be deleted.

Note: Important to say that some feature as Filtering are for Logging 5.9, then, not supported in Logging 5.8 and they shouldn't be included in the documentation in OpenShift 4.17.

[0] https://access.redhat.com/support/policy/updates/openshift_operators