Based on the idea of @jazzyisj in this post, I created another custom template for German text. I use the macros for TTS as well as phone notifications. See the repository for some examples.
It contains some macros for formatting words in singular or plural based of a given quantity and also a macro for converting arrays into comma-separated lists (just like @jazzyisj’s version), but with the German “und” instead of “and”.
You can install it via HACS as a custom repository. I also submitted it to be included with HACS by default and will update you if it gets approved.
Your feedback and suggestions for more German formatting macros would be welcome.