I just downloaded and started the raspberry KivyPie impage from here

According to the documentation, it is PipaOs/Raspbian based.

How can I change the keyboard language to German?

I tried

sudo dpkg-reconfigure keyboard-configuration

this works (at least it asks me all kind of keyboard questions)

at the end, the warning

update-rc.d: warning: start and stop actions are no longer supported

appears twice. The keyboard layout does not change, not even after a reboot.

Any idea how this is fixable?

I currently have no internet on that pi and raspi-config is not avaible on that image