In Germany they are called Kartoffeln (which is also a slur for the Germans itself).
But potatoes are also called ErdΓ€pfel (ground apples) or in southern dialect Krombire (bent pear).
More variants here:
Source (German): https://die-kartoffel.de/wissen/schon-gewusst/kartoffel-deutsche-dialekte/
Semi.
Another kind of slur is calling "spieΓig" (dunno the english word. Google suggests stuffy or bourgeois) Germans "Almans" which is essentially the french word for german people but if you call a german "Alman" it's kinda an insult (unless you own it).
Edit: I just noticed what a grammatical nonsense I wrote. :p