No there are no visible query strings, but I realized some interesting Request Headers (:authority :method :path and :scheme) in this environment. See: Hypertext Transfer Protocol version 2.0
So for example for a subpage the values are
:authority: domain.de
:method: GET
:path: /unternehmen
:scheme: https
Maybe the :path request Headers causes $request->data() not to be empty? But i think i’m not able to remove these kind of request headers.
Ok. I could not found if it had to do with the pseudo-header :path in h2 environment. So the URL did not contain any visible GET parameters. So I think it has to do with the :path request header. For me it made absolutely no sense to have $_GET param that is equal to the current URL path. So I was able to get around this by a kirby hook: