"Referrer-Policy" not right

Nextcloud-Version: 18.0.3
Webserver: Apache 2.4.25
OS: Debian Stretch

Get error “Referrer-Policy” not right in Nextcloud Dashboard on Security issues.

  • the error accoured now again with Update from 17 -> 18
  • before (I think with NC14 or so) the error ocurred already once and I put the headers section in Apache config, then it was ok
  • I read all related topics in the forum, that suggest a lot of things, all did not work
  • required mods are enabled
  • apache config as follws (with alias, not as vhost, but same for all domains):
<IfModule mod_headers.c>
      Header always set Strict-Transport-Security "max-age=15552000; includeSubDomains"
      Header always set Referrer-Policy "no-referrer"
      Redirect 301 /.well-known/carddav /nextcloud/remote.php/dav
      Redirect 301 /.well-known/caldav /nextcloud/remote.php/dav
      Redirect 301 /.well-known/webfinger /nextcloud/public.php?service=webfinger
      Redirect 301 /ocm-provider/ /nextcloud/ocm-provider/
      Redirect 301 /ocs-provider/ /nextcloud/ocs-provider/

Any more suggestions? Thanks in advance.