@MichalKleiner docker nginx-proxy has 2 modes how to forward connection. default is to connect with http.

Hello, we have similar setup, SSL connection to Nginx reverse-proxy and then HTTP connection to Apache server. All projects configured with (SS3) Director.alternate_protocol = 'https' to generate proper links. SS4 simplified configuration and all you need is to set SS_BASE_URL to external url.

ahh, now I remember, once I've got that recursion error that was actually coming from public/.htaccess with RewriteBase /public but vhost was properly configured to serve public folder.

if silverstripe.log does not help, then you need to configure proper php error log.