I think you need some additional nginx config with proxy_… parameters.
I haven’t used with docker but I have gotten streamlit/nginx/https working in a Windows VM using tips from this post 112.  I believe the following nginx config was what fixed the … connecting … timeout issue for me.
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $host;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_read_timeout 86400;