Right, I have no problem connecting from the app docker container. My problem is connecting directly to the postgres DB from my local machine (so I can use pgAdmin) or from a cloud data processor like Stitch. Both of these expect a host IP address and SSH credentials, but I haven’t been able to get them to work (I get the error I showed above).
The only thing I’ve been able to do is use docker-ssh to access the app docker container directly (via publicKey) from my local computer (without doing launcher enter app), but I still need to do su postgres 'psql discourse' in order to access the DB, which I assume is the problem with pgAdmin/Stitch—they expect a direct connection.