hyphenation warning with language variants and polyglossia

[jspitz]

From https://github.com/reutenauer/polyglossia/issues/663:

I have a issue with a document, using the austrian language. Here is a minimal example file:

\documentclass{scrreprt}

\usepackage{polyglossia}
\setdefaultlanguage[variant=austrian]{german}
\usepackage[backend=biber]{biblatex}

\begin{document}
Hier steht Inhalt. Welcher jährlich mehr wird.
\end{document}

The run of lualatex gives the following warnings:

(/usr/share/texmf-dist/tex/latex/biblatex/lbx/german.lbx
Module polyglossia Warning: Language naustrian not found in language.dat.lua on
 input line 580

Package biblatex Warning: No hyphenation patterns for 'naustrian' on input line
 580.

) (/usr/share/texmf-dist/tex/latex/biblatex/lbx/german.lbx
Module polyglossia Warning: Language naustrian not found in language.dat.lua on
 input line 580

Package biblatex Warning: No hyphenation patterns for 'naustrian' on input line
 580.

)
Module polyglossia Warning: Language naustrian not found in language.dat.lua on
 input line 20

Package biblatex Warning: No hyphenation patterns for 'naustrian' on input line
 20.

)

The same file without austrian variant \setdefaultlanguage{german} gives no warnings. Versions are LuaHBTeX 1.18.0, polyglossia 2024/03/07 v2.1, biblatex 2023/03/05 v 3.19

---

AFAICS this is due \DeclareHyphenationExceptions. Interestingly, replacing them with \DefineHyphenationExceptions{ngerman} does not seem to fix it.

(These exceptions themselves are disputable in the lbx files; but I think these go back to plehmann)