'trusted_proxies' => ['127.0.0.1', '172.17.0.1'], # Die IP des Docker-Hosts
  'overwriteprotocol' => 'https',
  'overwritehost' => 'deimon-web.ddns.net',
  'overwritewebroot' => '/nextcloud',
Config file has leading content, please remove everything before "<?php" in config.php