The job diagnosis indicates that the underlying library Deepspeech requires libstdc++6, as indicated here: https://deepspeech.readthedocs.io/en/latest/SUPPORTED_PLATFORMS.html#linux-amd64-without-gpu.
I understand that you are running the latest version of the plugin (0.3) which relies on Deepspeech 0.9.1.
One option is to revert to an older version of the plugin, with an older version of Deepspeech, which works with older versions of libstdc++6. You can find this version here: https://update.dataiku.com/dss/8.0/plugins/speech-to-text-cpu/0.1.0/dss-plugin-speech-to-text-cpu-0....
Then, you can follow the steps of this post: https://update.dataiku.com/dss/8.0/plugins/speech-to-text-cpu/0.1.0/dss-plugin-speech-to-text-cpu-0....to reinstall.
Otherwise, you will need admin (sudo) access to the server hosting Dataiku DSS in order to update libstdc++. If you have this access and would like to pursue this quest, I would kindly ask which operating system the server runs on to guide you through these operations.