Changing keyboard layout/language to German on Armbian/Bookworm highly erratic

I've had two Cubietrucks running almost flawlessly for about 10 years on Armbian/Buster and previous versions. I recently decided to install Bookworm using Armbian_23.8.1_Cubietruck_bookworm_current_6.1.47.img.xz. On this I encountered several problems, whose causes I never fully uncovered, but got over them.

One of these problems was that neither manual setup nor the use of armbian-config allowed for a lasting configuration of the German keyboard layout, although "Personal Setting" says the opposite (see att. image No.2).  It's a pain in the neck, really.
All I could filter out is a commandline message that's only visible a second. See the last screenshot with four lines saying

I spent a long time figuring out what this means. I simply re-installed the relevant packages via "apt-get" hoping this would help, but there was no obvious change. At some stage of my manifold attempts I suddeny noticed that the keyboard had changed to German on the CT_1. However, I couldn't recall what had caused the change. So I approached my CT_2 and now I'm stuck again with the same issue. 😒

I wonder if others have experienced the same and were more competent in finding a way out. If so, please let me in on your secrets. 🙏