Sorry, I forgot to include hub_connect_ip in my sample. It was set to the ip of the docker0 interface, 172.17.0.1. I tried switching between DockerSpawner and SwarmSpawner on that node, but still got the same redirect loop error. I have read other posts that say that this problem can be solved by connecting to port 8000 for the interface, and I have left this as default, but connecting to that port yields no data.
> nc -zv 10.32.5.19 8000
Connection to 10.32.5.19 port 8000 [tcp/irdmi] succeeded!
> curl http://10.32.5.19:8000/
curl: (52) Empty reply from server
However, I just tried https://10.32.5.19:8000, and it works correctly! This also means my certificate key is working correctly. I will mark this issue as solved.