Get Graphana iframes to work via external nabu casa https: and internal http:

I have searched a lot, but I cannot find a solution. Perhaps somebody here can help or point me to existing resolutions…

So, I have graphana dashboards I want to integrate into HA as iframes. I also have the home assistant connect form nabu casa with my personal URL (lets call it my.url.com).

This is my graphana configuration:

plugins: []
custom_plugins: []
env_vars:
  - name: GF_SECURITY_ALLOW_EMBEDDING
    value: "true"
ssl: false
certfile: fullchain.pem
keyfile: privkey.pem

And this is my iframe (slightly masked):

type: iframe
url: >-
  https://my.url.com/api/hassio_ingress/yqAXXXXn2JubznXXXXynVimXXXXkcXXXXvs_F_MF4wc/d-solo/feXXXXXXXXXq8d/dashboard-name?orgId=1&timezone=browser&panelId=1&__feature.dashboardSceneSolo

It works well accessing it via my external URL, it does not work via my internal IP though. I kind of understand that I might need the NGINX addon to make it work. But as I have installed the sub domain (MY.url.com) via the nabu casa mechanism, I cannot find any howto to make this work. They all seem to rely on a duckdns installation.

Thanks a lot for any hints!