Unable to update operator from 12 to 13

Having Keycloak installed from OperatorHub, an automatic update from 12 to 13 took place. However, the update fails:

error validating existing CRs against new CRD's schema: keycloaks.keycloak.org: error validating custom resource against new schema &apiextensions.CustomResourceValidation{OpenAPIV3Schema:(*apiextensions.JSONSchemaProps)(0xc0051a4200)}: [].status.externalURL: Required value

Also, as there is only one channel (alpha), there is no way to revert back to v12.