Diego is correct that we added a SFTP handler, and it uses jsch library currently. However, the end point only supports username/password authentication at the moment. It doesn't support private key currently. If you need that as an option, you'll need to build your own handler. We support that via automation scripts (documentation here: https://ibm-maximo-dev.github.io/maximo-autoscript-documentation/integration/endpointhandler )
I would also open an idea for private key support in the SFTP client here: https://ibm-ai-apps.ideas.ibm.com/ideas