Broken LC_CTYPE in nds_DE locale

Hi,

I'm using Ubuntu MATE 21.04 with the Low German (nds_DE) system locale. With the default settings for this locale I'm unable to type non-ASCII characters such as äöüß in many applications.
Some research shows that /usr/share/i18n/locales/nds_DE defines LC_CTYPE to en_DK which looks very weird. Manually exporting LC_CTYPE=de_DE.UTF-8 fixes the bug for me.

I don't see why this is not the default setting. Most other LC_* variables use the de_DE definition by default in nds_DE. Is this a bug, or is there a reason why it's done this way?

Best regards and thanks in advance :)

P.S. I hope this is the right place for this topic; if not, please feel free to point out where this belongs. The ubuntu package search told me my locales are provided by the package `locales` which is provided by package `glibc` version `2.33-0ubuntu5`.

P.P.S. I'm also surprised that the locale definition uses the localized language name "Neddersass'sch" although "Plattdüütsch" and "Plattdütsch" are far more common forms. Nice to speak a language that can't decide on it's own name. But that just as a side note :)