Dear Maintainer,
The following program :
=========================================================================
\documentclass[12pt]{article}
% \usepackage[default]{fontsetup}
% \usepackage[olddefault]{fontsetup}
% \usepackage[cambria]{fontsetup}
% \usepackage[concrete]{fontsetup}
% \usepackage[ebgaramond]{fontsetup}
% \usepackage[erehwon]{fontsetup}
\usepackage[euler]{fontsetup} fails on \symbf undefined.
% \usepackage[fira]{fontsetup}
% \usepackage[gfsartemisia]{fontsetup}
\usepackage[gfsdidotclassic]{fontsetup}
% \usepackage[gfsdidot]{fontsetup}
% \usepackage[gfsneohellenic]{fontsetup}
% \usepackage[kerkis]{fontsetup}
% \usepackage[libertinus]{fontsetup}
% \usepackage[minion]{fontsetup}
% \usepackage[msgaramond]{fontsetup}
% \usepackage[neoeuler]{fontsetup}
% \usepackage[oldstandard]{fontsetup}
% \usepackage[palatino]{fontsetup}
% \usepackage[stixtwo]{fontsetup}
% \usepackage[talos]{fontsetup}
% \usepackage[times]{fontsetup}
% \usepackage[xcharter]{fontsetup}
% \usepackage[sansdefault]{fontsetup}
\usepackage{physics,tensor,bookmark}
\begin{document}
\def\ii{\symrm{i}}
\def\pp{\symrm{\pi}}
\begin{itemize}
\item Covariant derivative:
\[
\nabla \symbf{X} = \tensor{X}{^\alpha_{;\beta}} \pdv{x^\alpha}%
\otimes \dd{x^\beta} = \qty(\tensor{X}{^\alpha_{,\beta}} +
\Gamma^{\alpha}_{\beta\gamma} \,%
X^\gamma) \,\pdv{x^\alpha} \otimes \dd{x^\beta}
\]
\item Einstein's field equations:
\[ G_{\mu\nu} \equiv R_{\mu\nu} - \frac{1}{2} R g_{\mu\nu} =
\frac{8\pi G}{c^4} T_{\mu\nu} \]
\item Schwarzschild metric:
\[
c^2 \dd{\tau}^2 = \qty(1-\frac{r_{\mathrm{s}}}{r}) \, c^2 \dd{t}^2
- \qty(1-\frac{r_{\mathrm{s}}}{r})^{-1} \dd{r}^2
- r^2 \underbrace{\qty(\dd{\theta}^2 +
\sin^2 \theta \dd{\varphi}^2)}_{\dd{\Omega}^2}
\]
\item Einstein--Hilbert action:
\[ S = \frac{1}{2\kappa} \int R \sqrt{-g} \dd[4]{x} \]
\end{itemize}
\end{document}
=========================================================================
fails to compile with `usepackage{euler}{fontsetup, with the following error :
=========================================================================
ERROR: Package fontspec Error:
--- TeX said ---
(fontspec) The font "ugmr8a" cannot be found; this may be but
(fontspec) usually is not a fontspec bug. Either there is a
(fontspec) typo in the font name/file, the font is not
(fontspec) installed (correctly), or there is a bug in the
(fontspec) underlying font loading engine (XeTeX/luaotfload).
For immediate help type H <return>.
...
l.5 \setmathfont
{Garamond-Math.otf}
--- HELP ---
No help available
=========================================================================
This seems to be a bug with the definitions used by the fontspec package : the
texlive-latex-extra *is* installed, and contains
/usr/share/texlive/texmf-dist/fonts/tfm/public/mathdesign/mdugm/ugmr8a.tfm
Lacking information on how to report directly to the author (which should be
the shortest way) or to CTAN, I'm reporting to you.
HTH,