Web Frame Card weird behavior

I am running OH 3.2.0.M3 inside a docker container.

I am fighting already an hour in displaying Grafana graphs inside MainUI, showing connection problems.
So I stepped back to a simple Web Frame Card, which I configured to connect to www.google.com.

The results are somewhat weird, when I set the value for the source URL to:
www.google.com → I get openhab displayed inside the window (own instance)

http://www.google.com or https://www.google.com → I get connection rejection

I was looking for the karaf log:set command to enable DEBUG for the MainUI but was not successful

Any guess what this can be?
The container runs with network: host.

I have also connected to the docker container:

docker exec -it openhab bash

and run curl with all combinations including grafana link. These are working as expected.

Found the problem: iFrame embedding needs to be enabled.

Seems that www.google.com prohibits this.

For my grafana problem I got the solution here:

Adapt grafana.ini

# set to true if you want to allow browsers to render Grafana in a <frame>, <iframe>, <embed> or <object>. default is false.
allow_embedding = true