The Libertine font project ceased to make new releases circa 2012
(you will probably already have noticed that the debian/watch file is
pinging a location that no longer exists).  The TeX Live people have
taken over maintenance; the version of these fonts on CTAN
(https://www.ctan.org/pkg/libertine/) is still labeled “5.3.0” but has
received significant changes relative to what’s in Debian right now.
These changes are particularly important for use in LuaLaTeX
documents; without them, every document that uses these fonts,
rendered with LuaLaTex, will spew warnings (listed below).  I _think_
these warnings are harmless unless you want to use certain fancy
typographic features, but I’m not sure, and the problems are
apparently significant enough that libertine.sty contains special code
to force use of TeX Live’s version of the fonts.  That special code
is, however, ineffective on Debian because the font files in
/usr/share/texlive/texmf-dist/fonts/opentype/public/libertine are just
symlinks to the files provided by the fonts-linuxlibertine package.
(This is why I’ve marked the bug as severity important.  I’m also
cc:ing the TeX maintainers.)

Please update the fonts in this package to the versions found on CTAN.
It would be reasonable to consider https://www.ctan.org/pkg/libertine
the new upstream, IMHO.

Hi Zack,

thanks for your report.
[...]

I think I will go back to shipping *our* version of the LL fonts - I
wasn't aware that the Libertine fonts project is so much dead.

Let us hear what the ll maintainers here suggest.

(But this will only happen after release of bullseye, since everything
is in deep freeze now).

Thanks

Norbert