> I'd be curious how far eXTeX gets with modern LaTeX documents in practice.
The LaTeX kernel requires some primitives [0] that are unlikely to be supported in a 15-year-old engine, so you probably won't be able to use any version of TeX Live newer than TL20.
The LaTeX kernel requires some primitives [0] that are unlikely to be supported in a 15-year-old engine, so you probably won't be able to use any version of TeX Live newer than TL20.
[0]: https://texdoc.org/serve/ltnews31/0#section*.29
[1]: https://repo.autonoma.ca/repo/keentype