Prenote: I know, that there are already some questions regarding the hyphenation of words containing accented letters with LuaTeX. However, I couldn't find one, that really targets my problem.
Using LuaLaTeX and babel I would like to correct hyphenation patterns using
% !TeX TS-program = lualatex
\documentclass{book}
\usepackage[no-math]{fontspec}
\usepackage[russian,main=ngerman]{babel}
\usepackage{libertine}
\begin{hyphenrules}{russian}
\hyphenation{пус-тын-ник} %normal version
%%\hyphenation{пус-ты´н-ник} %first try
%%\hyphenation{пус-т\'ын-ник} %second try
\end{hyphenrules}
\begin{document}
\selectlanguage{russian}
\showhyphens{пустынник}
\showhyphens{пуст\'{ы}нник пуст\'ынник пусты´нник}
пуст\'{ы}нник пуст\'ынник пусты´нник
\end{document}
I correctly get пус-тын-ник for the "normal version". However, I could not figure out any combination to get an accented ы and the wanted hyphenation пус-ты´н-ник.
While the three alternatives пуст\'{ы}нник, пуст\'ынник and пусты´нник all look the same (at least using my project's font "Newton"), the hyphenation always gives me пу-сты-́н-ник, пу-сты-́н-ник and пу-сты´нник when using the line "first try" or "second try".
How can I get a correct hyphenation?
