Hello Dennis,
I stumbled across the same question. To use SSH, Openssh would need to be installed in Docker first. But this is not the recommended way, as the Docker image you are using does not provide this in its "original" version and you are extending it beyond its original purpose.
The cleaner way in this case would be to create your own Docker image tailored to your needs. Or if you only want to run commands, use the Unraid command line for Docker. More information can be found at: https://phoenixnap.com/kb/how-to-ssh-into-docker-container
Best regards
Dirtrunner
