+\begin_preamble
+\@ifpackageloaded{fontspec}{%
+ % Unicode fonts, nothing to do
+}{% setup Unicode with 8-bit LaTeX fonts:
+ % character-providing packages are not auto-loaded with "utf8-plain"
+ \usepackage{textcomp}
+
+ \ifdefined\XeTeXinputencoding
+ % XeTeX in legacy mode
+ \XeTeXinputencoding "bytes" % current file
+ \XeTeXdefaultencoding "bytes" % included files
+ \let\origUmathchar\Umathchar
+ \let\Umathchar\@undefined
+ \usepackage[utf8]{inputenc}
+ \let\Umathchar\origUmathchar
+ \fi
+ \ifdefined\directlua
+ \usepackage[utf8]{luainputenc} % must come after textcomp!
+ \else
+ \usepackage[utf8]{inputenc} % default since TeXLive 2018
+ \fi
+ % set up macro for INFINITY Character '∞'
+ \DeclareUnicodeCharacter{221E}{\ensuremath{\infty}}
+}
+\end_preamble