Followed the one-line Docker install for OSX:
docker run --name mattermost-preview -d --publish 8065:8065 mattermost/mattermost-preview
Which installed fine. Now docker ps reports:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
e2bdbdedfda7 mattermost/mattermost-preview "/bin/sh -c ./docker-" 5 minutes ago Up 4 minutes 3306/tcp, 0.0.0.0:8065->8065/tcp mattermost-preview
But nothing serves in browser to 127.0.0.1:8065 or 0.0.0.0:8065 or localhost:8065. Am I missing something?