Just an observation from a first time EE user (or pretty recent at that).
There’s something in your common/locations.conf that breaks proxying of websockets i.e. node js apps et al. Don’t really have the time to figure it out and I realize EE may not officially support node (feature request there). Anyway, have a look. It breaks node, meteor and a bunch of other frameworks reliant on websockets.
Used ee site create --html thinking it would work but no luck. This is on your latest 3.0.4 build.