Removed the symbolic link in the example file.

lualatex.tex

-% This file is just a symbolic link to the xelatex.tex file.
-\input ./xelatex
+\documentclass{beamer}
+  \usetheme{fibeamer}
+  \usepackage{polyglossia}
+  \setmainlanguage{english}
+  \usepackage{amsmath}   % `\equation`s
+  \usepackage{tabularx}  % Tables
+  \usepackage{booktabs}
+\begin{document}
+  \title{My Presentation}
+  \subtitle{Daring the Unknown}
+  \author{Jane Doe}
+  \frame{\maketitle}
+
+  \begin{frame}{Foo}{bar}
+    Hello world!
+    \begin{equation}
+      \tag{Mass--energy equivalence} e=mc^2
+    \end{equation}
+    \begin{center}
+      \begin{tabularx}{\textwidth}{lllX}
+      \toprule
+      Day & Min Temp & Max Temp & Summary \\
+      \midrule
+      Monday & $11^{\circ}\mathsf{C}$ & $22^\circ\mathsf{C}$ & A
+      clear day with lots of sunshine. However, the strong breeze
+      will bring down the temperatures. \\
+      \bottomrule
+      \end{tabularx}
+    \end{center}
+  \end{frame}
+\end{document}