I have haproxy running in opnsense system. Opnsense offloads the SSL and passes the connection nextcloud, which is located in the docker container. Is there any possibility to pass real client IP address to this nextcloud setup?
You need to do it like the nginx plugin does that automatically: Add headers like X-Real-IP and X-Forwarded-For
See: https://docs.nextcloud.com/server/15/admin_manual/configuration_server/reverse_proxy_configuration.html