@jens I think i worked it around on spring data end.
If someone is interested:
You’d need to override couchbaseTemplate in couch base config and pass your own instance of MappingCouchbaseConverter that has typeMapper created with custom DefaultCouchbaseTypeMapper. Unfortunately typeMapper property is protected and does not have a setter, so you’d have to extend MappingCouchbaseConverter in order to change it.
Thank you for your help @jens
Leo