I'm facing same issue. When I try to create table through spark.sql I'm getting the same "schema not found" message.

Configuration is basically the same:

spark.jars.packages io.unitycatalog:unitycatalog-spark_2.12:0.2.0,io.delta:delta-spark_2.12:3.2.1
spark.sql.extensions io.delta.sql.DeltaSparkSessionExtension
spark.sql.catalog.spark_catalog io.unitycatalog.spark.UCSingleCatalog
spark.sql.catalog.t_clean io.unitycatalog.spark.UCSingleCatalog
spark.sql.catalog.t_clean.uri http://localhost:8080
spark.sql.defaultCatalog t_clean
spark.sql.catalog.t_clean.token