I forget about the stupid case sensitive username thing.
I need to change the port OctoPrint is listening on on OctoPi because I want to do a port forward and that port is already used in my router!
Please be more precise. What does "broke my web authentication" mean? What kind of error are you seeing? How exactly does your haproxy configuration look like now? Also share
"It broke" isn't enough information for anyone to help you.