OK, thanks! Now I know, where to start.

NodeBB has the ability to add content to the header section via Nodebb admin. If I do this, the content is shown at (1). This works easy, but I'm looking for an option to add some content before the header (2). Is there a simple way to do this (i couldn't find one) like a plugin, or do I have to edit the theme template?

Thanks,
Christoph

I got it to work... I changed the .htaccess to

RewriteEngine On
RewriteCond %{HTTP_HOST} ^forum.example.com
RewriteRule ^(.*)$ http://localhost:61111/$1 [NC,P,L]

and the config.json to

{
    "url": "http://forum.example.com",
    "port": "61111",
    "secret": "###",
    "database": "redis",
    "redis": {
        "host": "/home/###/.redis/sock",
        "password": "",
        "database": "0"
    }
}

@mono Have you been able to solve the last issue? Right now I' trying to install nodebb on uberspace, too. I got it working until I get to the output which is shown in your screenshot. It looks like the nodebb task can find the stylesheet etc:

25/11 13:45 [19111] - info: NodeBB Ready
25/11 13:45 [19111] - info: Enabling 'trust proxy'
25/11 13:45 [19111] - info: NodeBB is now listening on: 0.0.0.0:61111
25/11 13:45 [19111] - verbose: [hotswap] Router with id `plugins` replaced successfully
25/11 13:45 [19111] - verbose: [plugins] All plugins reloaded and rerouted
25/11 13:45 [19111] - verbose: [hotswap] Router with id `auth` replaced successfully
25/11 13:45 [19111] - verbose: [meta/css] stylesheet.css committed to disk.
25/11 13:45 [19111] - warn: Route requested but not found: /
25/11 13:45 [19111] - warn: Route requested but not found: /stylesheet.css?181d247a-2130-4c3e-aae2-d8524b85dbad
25/11 13:45 [19111] - warn: Route requested but not found: /plugins/nodebb-plugin-markdown/styles/railscasts.css
25/11 13:45 [19111] - warn: Route requested but not found: /nodebb.min.js?181d247a-2130-4c3e-aae2-d8524b85dbad
25/11 13:45 [19111] - warn: Route requested but not found: /nodebb.min.js?181d247a-2130-4c3e-aae2-d8524b85dbad

Did you find a solution?

Thanks
Chrissss