I try to use Russian in a \foreignlanguage entry.
So here is what I e.g. write:
\foreignlanguage{russian}{Федеральная служба по надзору в сфере связи, информационных технологий и массовых коммуникаций}
Now, as my main document contains several other languages (main language is German), I'll add this to babel and isodate:
\usepackage[norsk, english, german, russian, ngerman]{babel}
\usepackage[norsk, english, german, russian, ngerman]{isodate}
\usepackage{lmodern} % font
And I need to install texlive-babel-russian (or similar depending on your Tex distro)
Also, of course my document always uses UTF-8:
% !TeX program = lualatex
% !TeX encoding = UTF-8
% !TeX spellcheck = de_DE
\documentclass[12pt,a4paper,titlepage,numbers=noenddot,oneside]{scrbook}
\KOMAoption{listof}{totocnumbered, leveldown}
% unicode
%\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[utf8]{luainputenc}
However, i get this error (and I don't get this one for any other language):
! Package isodate Error: Isodate definition file russian.idf not found.
See the isodate package documentation for explanation. Type H for immediate help. ...
l.79 \ProcessOptions*
Maybe you misspelled the language option?
Edit:
If I look in /usr/share/texlive/texmf-dist/tex/latex/isodate there is indeed no definition for Russian in there.
So I've just removed russian from isodate it compiles, at least.
However it can still not display any characters in Russian?
russianas an option toisodate? I.e.\usepackage[norsk, english, german, ngerman]{isodate}. I wouldn't have thought you need it unless you want to print the date in Russian. – moewe Jun 22 '20 at 18:15\usepackage[T1]{fontenc}. With LuaLaTeX\usepackage[utf8]{luainputenc}is pretty pointless since LuaLaTeX assumes UTF-8 input anyway. – moewe Jun 22 '20 at 18:16\usepackage{libertinus}, which loads Libertinus. – moewe Jun 22 '20 at 18:22