SQLNonTransientConnectionException with port 3306 strongly points to egress being blocked from your Databricks compute to the default Hive Metastore (which runs on Azure Database for MySQL). Databricks recently published the reserved IP ranges and guidance for allowlisting the metastore endpoints; if your firewall / UDRs still have the old IPs or only allow specific ranges, you’ll see exactly this error.

https://community.databricks.com/t5/product-platform-updates/ip-cidr-for-azure-databricks-hive-metas...