How do I get ligatures and guillemets with Libertine and PDFLaTeX?

Question

I want:

• my document to be rendered in the Libertine (or Libertinus) typeface with all the default ligatures enabled (including Th and Qu);
• use guillemets (»«) and other special characters directly in the text;
• those guillemets to be rendered properly (and not as some resized ≪);
• to compile my document with PDFLaTeX.

My best attempt at this is:

\documentclass[border=3pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage[OT1]{fontenc}
\usepackage{libertine}

\begin{document}
»Thesaurus frisst Quastenflosser!«
\end{document}

This produces the desired result, except for using fake guillemets, instead of Libertine’s:

What I want is:

How can I achieve this? I tried combinations of different options (such as T1) for fontenc or disabling it and babel to no avail.

There are several similar questions, but the solutions all use macros for the guillemets or XeLaTeX, which I am well aware of but cannot or do not want to use.

Answer 1

Sadly, T1 encoding and Libertine ligatures do not work together when using pdftex. Using the OT1 encoding will give you the nice ligatures but will suppress hyphenation and break kerning in any word containing an umlaut or a ß, and will prevent any possibility of copy/pasting or searching for text in the final PDF document. Note also that not all automatic ligatures are meaningful, and you might need to break some of them manually: for example, OT1 Libertine has a "fb" ligature which in most cases is not desired.

This being said, it is relatively easy to achieve what you want, and

\documentclass{article}

% \usepackage[OT1]{fontenc} % is the default anyway
\usepackage[utf8]{inputenc} % not really necessary since 2018
\usepackage{libertine}

\usepackage[ngerman]{babel}

\usepackage{newunicodechar}
\newunicodechar{»}{{\fontencoding{T1}\selectfont\guillemotright}}
\newunicodechar{«}{{\fontencoding{T1}\selectfont\guillemotleft}}

\begin{document}

»Thesaurus frisst Quastenflosser!«

\end{document}

will give the desired output

However, I must remark again that the drawbacks of using an OT1 encoded font are enormous when writing in German. Since I don't think that the Th and Qu ligatures are soooo common in a normal text, I would rather use the T1 encoding and define a macro for the desired ligature, e.g. something like

\newcommand*{\Qu}{{\fontencoding{OT1}\selectfont Qu}}