newpx makes fontspec fail

Question

If I use the newpx package and then load fontspec and try to select a font it fails. See the minimal example below.

The files (compiled with lualatex) for which fontspec font selection fails (by loading newpx before fontspec) with TeX Live 2021 and the packages up to date (via tlmgr) today (2022-03-28) used to work with an earlier TeX Live version (TeX Live 2020, or 2021 but with older versions of the packages, I can't tell exactly when).

I can't tell if the problem is due to newpx or fontspec (or luaotfload or something else).

Could you help me identify the cause, find a workaround and tell me who to report the problem to so that it can be fixed?

Thanks and have a nice day

%%%% MWE

\documentclass{scrartcl}

\usepackage{newpxtext}  % comment newpx and everything is ok
% this used to work with an older version of TeX Live (older version of the packages)
\usepackage{fontspec}
% \usepackage{kurier}  % not needed

\setmainfont{texgyrebonum-regular.otf}  % font selection by file name gives no error but does not select the correct font: newpx font (TeXGyrePagellaX) used instead of TeX Gyre Bonum

\setsansfont{Kurier}  % font selection by font name gives a fontspec error: "The font (Kurier, or any other font selected by font name) cannot be found"

\begin{document}

ABCXYZ

\end{document}

%%%%

Answer 1

The problem should be reported to the newpxtext author, but you also shouldn't load the newpxtext package if you don't actually want to use it's font.

The reason that font loading fails after \usepackage{newtxtext} is that newtxtext executes \defaultfontfeatures with a bunch of features which really only apply to it's own font, but since they are set as a default they affect all further loaded fonts. Especially it sets the option Extension = .otf specifying that all following names should be interpreted as filenames of .otf files.

The best fix is not to load newpxtext but you can also fix the \defaultfontfeatures issue by resetting the default font features: Add \defaultfontfeatures{} between loading newpxtext and loading another font.

This still leaves the issue that your font change does not actually get applied. That's because the newpxtext package expects that it's only loaded when it should actually control the font and therefore changes the font only in \begin{document} probably to stop the preamble from interfering. You could probably avoid that by moving \setmainfont after \begin{document} but at that point you are going through a lot of trouble just to load a package you don't actually want to use...

Answer 2

If you want to use a version of Palatino with fontspec, use

\setmainfont{TeX Gyre Pagella}

or

\setmainfont{Domitian}

Both of these are clones of Adobe’s Palatino. You can also use a version of Palatino that you have installed on your system, such as Palatino Linotype with Microsoft Windows or Office.

If you also want to replace newtxmath, load unicode-math and then use either

\setmathfont{TeX Gyre Pagella Math}

or

\setmathfont{Asana Math}