I have been using XeLaTeX (TeX Live on Linux) for several years and two dashes have always been turned into an en-dash. For some time now (maybe since I installed TeX Live 2023) this doesn't happen anymore:
\documentclass{article}
\usepackage{fontspec}
%\defaultfontfeatures{Mapping=tex-text} % does not work
%\defaultfontfeatures{Ligatures=TeX} % does not work
\setmainfont{STIXTwoText-Regular.otf}
\begin{document}
Two hyphens -- are not automatically replaced by an en-dash \textendash.
Three hyphens --- are not automatically replaced by an em-dash \textemdash.
\end{document}
Everything is fine with LuaLaTeX, but I'd rather use XeLaTeX :) Any suggestions?

XeandLuaLaTeX, can you update yourTeXdistributions – MadyYuvi Oct 06 '23 at 13:56tex-text: you should see some warning. – egreg Oct 06 '23 at 14:08