Bad Request (400)
I built a virtualbox image using freedom-maker which included plinth v0.3.2.0.git.20140829-1. I ran the image in virtualbox using the network configuration from https://wiki.debian.org/FreedomBox/VirtualBoxImages. When I go to https://192.168.1.1/plinth in the browser on the host system, I get Bad Request (400).
I found that I could access jwchat and static pages (like https://192.168.1.1/plinth/static/theme/readme.md), so I think the problem is only with the pages being served by plinth and proxyed through apache.
I found one solution to this problem which is to add '192.168.1.1' to the ALLOWED_HOSTS setting in plinth.py. After restarting plinth I am able to access it. I'm not sure if this change is the best solution or even a complete solution though (are there other hosts we might want to access it over?).