Debezium only returns unknown data types in Postgres as a string of the java hash code (ex: [B@1ef41123). At run time the string of the value is available from the wal, but it is using SchemaBuider.bytes() and converting using the convertBinary() method. If SchemaBuilder.string() and convertString() are instead used, the human readable text is returned. Tested with shouldGenerateSnapshotsForCustomDatatypes()
Proposal is for the human readable string be either the default behavior or an option for unknown data types. Currently this is desired specifically for partially supporting enumerations as that is not a feature of debezium-postgres.