@Rob Myers​ Just curious to know, have you migrated all your data into new metastore from hive_metastore. because hive_metastore that you are seeing is just not a part of unity catalog meta store, it is just mounted, and we won't be benefited with all security features that unity catalog provides until you upgrade your tables from legacy hive. coming to your question to change default catalog please try to use below config and see spark.databricks.sql.initial.catalog.name hive_metastore

Not migrated - this is a new instance scratch.

I can't set that parameter for SQL warehouses.

@Rob Myers​ please login to SQL --> SQL Admin Console --> SQL Warehouse Settings (SQL Config parameters and try ) , if not use any warehouse and open sql editor and set below query

%sql

SET spark.databricks.sql.initial.catalog.name = hive_metastore;

Unfortunately neither of those work, dont think that parameter has been allowed for setting in SQL warehouses.

Also on a general purpose cluster is denied as it is a static configuration which needs to be done at start up.