Hi Warren.
You should be selecting the driver labeled “MS SQL Server/Sybase” in the dropdown, not the one labeled "MS SQL Server."
The former is for the freetds driver. The latter for sqlsrv driver (which is used only on Windows systems.)
You will also need to change the connection string it generates. Where is says mssql, replace it with dblib. This is a bug that is fixed in development and will be pushed to production soon.