[Tex/LaTex] How to disable L3 programming layer

latex3texlivetexlive-2019

I have a xmltex development project which runs on my office computer with texlive 2019, but not on my home computer with a (just now) installed texlive 2019. I noted that the recent texlive uses some LaTeX3 packages by default which the slightly older version does not.

The first few output lines of the newer texlive:

This is pdfTeX, Version 3.14159265-2.6-1.40.20 (TeX Live 2019/Debian) (preloaded format=latex)
 restricted \write18 enabled.
entering extended mode
(./main.tex
LaTeX2e <2020-02-02> patch level 2
L3 programming layer <2020-02-14> (./xmltex.tex

That last line does not appear in my slightly older work machine:

This is pdfTeX, Version 3.14159265-2.6-1.40.20 (TeX Live 2019) (preloaded format=latex)
 restricted \write18 enabled.
entering extended mode
(./main.tex
LaTeX2e <2018-12-01>
(./xmltex.tex

Somehow the l3backend-dvips.def seems to be incompatible with xmltex.tex, so the question is:

Is there a way to disable the "L3 programming layer" on the more recent texlive installation?

edit:

the actual error message that appears on my home machine is:

(/usr/share/texlive/texmf-dist/tex/latex/l3backend/l3backend-dvips.def

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.1 %
     %
? x
No pages of output.

The l3backend-dvips package is not attemtped to be included on the other, older, machine.

edit 2
I was asked for a MWE… Since the L3 programming layer-line and the automatic inclusion of the l3backend package, both of which i want to get rid of, are independend from any input, this will do:

main.tex:

\documentclass{article}

\begin{document}
Test
\end{document}

latex run is 

latex main

edit3: (i removed the xmltex example because it was not really showing the original error but another one, which i noticed too late. Sorry.)

Again: my question is how i can prevent LaTeX from including any L3 packages in the most recent versions of texlive?

Best Answer

To answer your question about deactivation ... the L3 programming layer is part of the core LaTeX format since release 2019-10-01 and it can't be deactivated. At the moment it is there to speed up processing of packages written in expl3, e.g., xparse, fontspec, and many others, but going forward core parts of LaTeX will make direct use of it.

Deactivation is only possible by using a release prior to 2019-10 (even rollback via "latexrelease" will load).

It is therefore important to understand why get the issue which should not be the case.

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