is there a way to talk to delta tables on the local filesystem through JDBC? or would I have to roll my own driver

Delta Lake is a storage format. You will still need some kind of query engine to reconstruct the state of the table, and to read the data that’s in the current state of the table. For this you will have to setup (or use a managed solution for) a query engine that supports Delta, such as Spark or Trino. Both of those offer a JDBC/ODBC interface.