You should be able to bind-mount that specific driver all the way into place, e.g.:
- ./jdbc/mysql-connector-j-8.3.0.jar:/usr/local/bin/ignition/user-lib/jdbc/mysql-connector-j.jar
By bind-mounting the entire folder, you effectively shadow the pre-existing files that are part of the image (such as the MariaDB, Postgres, and MSSQL JDBC drivers, as well as the commons-dbcp2 and commons-pool2 JARs).