In the german account templates 'common' and 'full' there are two wrong spellings, which was fixed in kmymoney by commit https://invent.kde.org/office/kmymoney/commit/8abae0ba775c8133d5f5fc928004740916e5646f
The error was initially reported at https://bugs.kde.org/show_bug.cgi?id=420016.
Thanks, I have fixed this for the upcoming release.
According https://de.wikipedia.org/wiki/Einkommensteuer#Nationale_Einkommensteuern we should also adjust de_AT, but not de_CH. Sorry I am too tired today, so reopening.
The same issue existed still in the program translation: https://lists.gnucash.org/pipermail/gnucash-de/2020-December/011924.html (commit 5f41e87) Fixed for AT in commit 60aeded. So the code should be fixed, but in the german guide, I see it, too.
Fixed in commit e4fef3f.