I think I posted about the German thing with potato salad before at some point, but I recently stumbled across a potato salad discussion on reddit and, well, it sums the thing up very nicely as there being one thing all Germans can agree on:
There should be potatoes in a potato salad.
All the rest? Depends. There's the dressing with mayo fraction, the dressing with oil and vinegar fraction, there's some that put in yoghurt. There's onions or not, radishes or not, cucumbers or not (and those pickled or not). Eggs. Bacon. Peas. Most people have a favourite version, often the one their gran or mom made (though if you ask me, the best one ever was the one my gran made. Even if others come close).
So if you ever wondered what a real German potato salad looks like, the answer is probably: Use potatoes, and whatever else you enjoy.
(My gran's version went like this: Marinade an onion, diced, in the pickle liquid of pickled cucumbers, the German style one pickled in vinegar and a bit of sugar. Add cubed pickled onions. Boil potatoes, peel, cut into slices, add to mixture. Add in hot broth and let cool until only warm, then add a little bit of mayonnaise, salt, maybe pepper. Once it's fairly cool, add a sliced, hard-boiled egg per person. Let cool off completely and serve.)