switch compiler pdflatex -> LuaLaTeX, cf.

https://claude.ai/chat/ad2ba988-ddf1-4334-a1b8-f29e5da256b1

presentation/config/header.tex

@@ -239,6 +239,7 @@ aspectratio=169,%  common values: 169, 1610, 43
 % \usepackage{fontawesome} % loads fancy web symbols 2016
 \usepackage{fontawesome5} % loads fancy web symbols 2022
 \usepackage{tipa}        % allows to use \textpipe (for adjustable symbol |)
+\usepackage{emoji}
 
 % % note: commented out bm cause suddenly and without any changes in the
 % offending document, led to error 'Too many math alphabets used in version

presentation/presentation.tex

+% !TEX program = lualatex
+% reason: using emoji package
+
 % input packages to load, custom user macros
 \input{config/header}
 \input{config/user_macros}
@@ -193,6 +196,8 @@
 \end{document}
 
 %%% Local Variables:
+%%% TeX-command-default: "LuaLaTeX"
+%%% TeX-engine: luatex
 %%% mode: latex
 %%% TeX-master: t
 %%% End: