I got the basic idea for my suggestion from my neighbour.
He cleaned his aquarium with the help of magnets (rag inside, magnet on the outside, see Cleaning the aquarium
That made me think about my kitchen drain.
The problem: The odour closure device and the kitchen drain leading into the wall are both rather flat.
That's why I have to clean them more often.
So, I talked my neighbour into giving me two of his awesome magnets and I used them in my kitchen.
Now, I have a No.
12 thin nut in the drain pipe (left) and one in the odour closing device (right).
There are two magnets on the outside of the pipes (they are held in place by the thin nuts).
The cleaning of the drain now entails a few spiral movements with the magnets and some heavy flushing.
Meaning: Unscrewing the pipe and removing dirt and sludge is only necessary in larger intervals.