Согласно сообщению Joseph Wright (member of the LaTeX Project, with a particular interest in
LaTeX3 development)
https://www.texdev.net/2024/11/05/engine-news-from-the-latex-projectЦитата:
The time to move to LuaTeX for new LaTeX documents is here. For existing pdfTeX sources, tagging will be available, although it may be more limited than for LuaTeX. pdfTeX users can keep their existing sources and will see tagging available. XeTeX users really do need to re-work their sources for LuaTeX.
Цитата:
The situation with XeTeX contrasts strongly with LuaTeX: although both are Unicode engines, XeTeX has none of the flexibility available in LuaTeX. There are significant technical limitations which mean that XeTeX cannot create accessible PDFs at all: this is unlikely to change. The engine itself is unmaintained, and with no access to internals, fixing the current issues alone would not really help. XeTeX does not produce PDFs directly, and that essentially rules out full tagging support (see below).