Can add Xiaomi Hub but not child devices (sensors)

Hi,
I have a Xiaomi hub v2 and a couple of child devices. E.g. Temperature sensors, window sensors, motion sensors, waterleak sensors etc.

I can successfully add the hub via the Xiaomi Miio integration and I can e.g. activate the alarm or the nightlight just fine. However it does not show any of my Child devices in HA.

Then I learned for those I need another integration the Xiaomi Gateway (Aqara) integration.
In the documentation it says I need to enter key and name during installation. However during the installation it asks me for IP address and MAC address. I am confused.

Also it links to a manual how I enable LAN access on the gateway. It says I need to change to region China Mainland. I have the hub and all the child devices setup in my region Germany. I did switch the region to China but then the app is completely empty. The hub is not there. When I switch back to Germany then everything is there again.

How can I enable LAN access? Is there another way?

Xiaomi Gateway (Aqara) integration,configure hub with ip+token