Top row on keyboard has a different behavior when pressing alt and using a non mac keyboard
Go to System Preferences &gt; Keyboard &gt; Input Sources and make sure the only item on the list is &quot;German Standard&quot; (and not &quot;German&quot;).
The Apple &quot;German&quot; input source puts [ ] { } on alt 5689, while the German Standard input source should put them on alt 8970, and there are various other differences, such as @ being on alt L for &quot;German&quot; instead of on alt Q for &quot;German Standard&quot;.
Because the differences are on the alt level, the printing on an Apple &quot;German&quot; keyboard can look the same as that on a &quot;German Standard&quot; keyboard, except perhaps for where @ appears as the 3rd item on a key. So it is easy to choose the wrong input source.