Dear all,
arabtex-doc.tex is currently (TL2021) located under:
texlive/2021/texmf-dist/tex/latex/arabtex/
which seems wrong to me. I think the right place is:
texlive/2021/texmf-dist/doc/latex/arabtex/
where also arabtex-doc.pdf resides.
Best, Arash