For version 1.0.3 and after which contains this patch (see parent task),

=== Start of requested changes ===
You can specify Velero loglevel in DataProtectionApplication resource as shown in the example below.

apiVersion: oadp.openshift.io/v1alpha1
kind: DataProtectionApplication
metadata:
  name: velero-sample
spec:
  configuration:
    velero:
      logLevel: warning

If you are on versions prior to 1.0.3 please upgrade to access this option.
=== End of requested changes ===

=== Below for reference only but do not document it downstream === Steps for 1.0.2 or older ===
For versions before you will have to modify velero deployments directly. Pre-requisite to this would be to reduce oadp-controller-manager deployment replica to 0 so it doesn't reconcile and override the changes.
https://docs.openshift.com/container-platform/4.8/backup_and_restore/application_backup_and_restore/troubleshooting.html#oadp-debugging-oc-cli_oadp-troubleshooting
before the steps mentioned after subheading "Velero pod debug logs" can proceed, the following prerequisites are required.

• Edit replica of openshift-adp-controller-manager deployment to 0 inside OADP ClusterServiceVersion
  You can do this from web interface by going to OpenShift Web Console Administrator view > Operators > Installed Operators > namespace > OADP Operator > YAML
  which is equivalent to navigating to <openshift-web-console>/k8s/ns/openshift-adp/operators.coreos.com~v1alpha1~ClusterServiceVersion/oadp-operator.v1.0.2/yaml (example link for oadp-operator version v1.0.2)
  
  You can do change the replica to 0 in CLI with

  oc patch $(oc get csv -n openshift-adp -oname | grep oadp) -n openshift-adp --patch '[{"op": "replace", "path": "/spec/install/spec/deployments/0/spec/replicas", "value": 0 }]' --type=json

If you need OADP Operator to process your DataProtectionApplication again set replicas back to 1.

oc patch $(oc get csv -n openshift-adp -oname | grep oadp) -n openshift-adp --patch '[{"op": "replace", "path": "/spec/install/spec/deployments/0/spec/replicas", "value": 1 }]' --type=json