Hello @danjenkins and welcome.
The docker image on github was experimental development and not something we are supporting yet. There are a number of docker images out there, I found this one GitHub - jakezp/emoncms particularly useful, but I haven’t tried it for a while.
We are also developing a build script that would be good to use to either inform or form the basis of a future docker image EmonSD build script progress update and beta release. But also works a treat in and of itself.