Trying to get a multi container setup using nginx (also in a docker container) to work with web sockets. There's a chance that the load balancer will also cause issues later. And the front end uses nuxt, which will probably also cause issues once we turn server side rendering on as well.
This is not really something I've studied deeply before.

I'm not having fun.

WebSockets usually need some extra headers set. Depending on your webapp you may need to add some extra header like "Origin" but it usually works without.

I'm using the below for a lot of my stuff..I set the proxy_pass and include that file or leave it (if I don't add any other entries). Be aware that default/global entries get cleared once you add new ones. This is why I have my default proxy stuff there as well.

Hope this helps.