How to set a fontseries in beamer?

Question

I'm trying to use font lato in a beamer presentation. Normal text should be using the light font (please, let's not discuss typography here -- I know). According to the font catalogue, I get it like so:

\fontseries{l}\selectfont

Extrapolating from how we can set "complex" font families (seen here), I tried this:

\documentclass{beamer}

\usepackage[default]{lato}
\usepackage[T1]{fontenc}

\setbeamerfont{normal text}{series=\fontseries{l}\selectfont}

\begin{document}
\begin{frame}
  Test\\
  {\normalfont Test} \\
  {\fontseries{l}\selectfont Test}\\
  \textbf{Test}
\end{frame}
\end{document}

But the result is not as expected:

There are no error messages.

How can I tell beamer to use the light font series?

I'm happy to accept solutiond for either pdflatex or lualatex.

Answer 1

The beamer source code says

\setbeamerfont{normal text}{} % ignored currently

So instead of trying to set the normal font template (which will be ignore anyway), you could set the font using \AtBeginDocument{\fontseries{l}\selectfont}

\documentclass{beamer}

\usepackage[default]{lato}
\usepackage[T1]{fontenc}

\AtBeginDocument{\fontseries{l}\selectfont}

\begin{document}
\begin{frame}
  Test\\
  {\normalfont Test} \\
  {\fontseries{l}\selectfont Test}\\
  \textbf{Test}
\end{frame}
\end{document}