A quick note on reverse proxies and SSL certificates
Installing an SSL certificate on a reverse proxy only encrypts the connection from the outside world to the proxy server. The encryption status of the connection to the destination host + port will be determined by how the reverse proxy entry is configured.
Example: if you're running Nextcloud on a server without a valid and properly configured SSL certificate, using a reverse proxy with a valid and properly configured SSL certificate will not encrypt the traffic from the reverse proxy to the Nextcloud host.