I had to read code to discover that the web UI (Postorious) server address doesn't exist in any config file.
To bind it to something other than localhost, you put the desired ip address & port on the
python manage.py runserver command line (in mailman-suite_project.
It must be an IP address - it doesn't resolve DNS names. The port is appended to the IP address with a ':'.
So, in venv 2.7
cd mailman-suite_project && python manage.py runserver 10.0.0.11:8000 will work.
There are all sorts of issues if your network is at all public, but in my case, a multi-machine walled garden, with no local web browser, it allowed bootstrapping to continue.
The runserver command also takes --ipv6 (or -6) to bind to an IPv6 address, --nothreading and --noreload also exist (but i haven't tracked down whethere they're useful')
Hope this saves someone else a lot of research...