Right regex expression

See if info here points you in the right direction:
https://stackoverflow.com/questions/3009993/regex-what-would-be-regex-for-matching-foreign-characters

Thanks.

I tried with /name/(?P<name>[a-zA-Z]+$/\p{L}), but it doesn’t work. What did I wrong?

some more info:
https://stackoverflow.com/questions/28156769/foreign-language-characters-in-regular-expression-in-c-sharp

I tried different solutions, but nothing worked..

I don’t think it’s possible to do what your are trying to do. Endpoint names should comply with slug/permalink restrictions, which do not include extended characters. You will notice that when you use extended characters in titles that the resulting permalink slug that WP generates will have diacritics stripped out. Your endpoints should be similarly named.