<?php
$CONFIG = array (
  "trusted_proxies"   => ['10.0.0.1'],
  "overwritehost"     => "ssl-proxy.tld",
  "overwriteprotocol" => "https",
  "overwritewebroot"  => "/domain.tld/nextcloud",
  "overwritecondaddr" => "^10\.0\.0\.1$",
);

https://docs.nextcloud.com/server/11/admin_manual/configuration_server/reverse_proxy_configuration.html#example