I have seen this and so on, but I seem to get compilation errors when trying to use foreigndisplayquote, which is basically just otherlanguage from babel and displayquote from csquotes.
The same error of course happens when I use that inline or so via \foreignlanguage{german}{daß}.
My document is in ngerman, i.e. "new" German language, but I'd like to quote a part in german, i.e. the old version, because well… that text is just so old. See here for the difference.
When I change that to another language I have loaded, e.g. english it works.
But the example below in my case throws an error like this one:
Your command will be ignored, type to proceed ! Package babel Error: You haven't defined the language en yet. See the babel package documentation for explanation. Type H for immediate help.
However, I did actually install the babel german language package (also tested online on overleaf etc.) and also added the language to babel, as you can see.
Simplified document:
% !TeX program = lualatex
% !TeX encoding = UTF-8
% !TeX spellcheck = de_DE
\documentclass[12pt,a4paper,titlepage,numbers=noenddot,oneside]{scrbook}
\KOMAoption{listof}{totocnumbered, leveldown}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[utf8]{luainputenc}
\usepackage[norsk, english, german, ngerman]{babel}
\usepackage[norsk, english, german, ngerman]{isodate}
\usepackage{lmodern} % font
\usepackage[german=quotes]{csquotes} % deutsche Anführunsgzeichen mit \enquote
\begin{document}
\begin{foreigndisplayquote}[german]
Daß ist ein alter Text.
\end{foreigndisplayquote}
\end{document}
TexLive 2019
inputencnorluainputenc: both do essentially nothing in your situation. – egreg Jun 17 '20 at 13:46inputencmay be omit table, writing many characters like…(one character) does not work, i.e. they are not printed in the PDF then. – rugk Jun 17 '20 at 14:42