Yes, I was hoping to avoid that, because of the security implications of giving the homeassistant docker container SSH access to the host. As well as the fact that I would need to give the homeassistant container the private SSH key (and would also need a SSH key without a passphrase, in order to execute it via a shell_command service).
I was hoping to do it using this method with a named pipe, but this method appears to use cronjob on the host. I’m not sure how it was achieved in that case.