Let’s assume the incident you referred is true. It’s still not the phone microphone that’s doing it, it’s the spyware/adware/malware app you installed from play store.
Solution? Degoogle and stay away from tech giants like meta, apple, etc. Use opens source alternatives.
If you are still paranoid, Android 13 and onwards, whenever your cam/mic is being used, you can see a green microphone or camera logo on the status bar top right.
I’m sure Germany is not a monolithic entity. It has different departments for different things and if you don’t agree with them politically or dislike their actions, none of that has anything to do with them using tech for general administration purposes.