~/.config/fontconfig/conf.d/01-liberation.conf

01-liberation.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
  <alias>
    <family>Liberation Sans</family>
    <default>
      <family>sans-serif</family>
    </default>
  </alias>
  <alias>
    <family>Helvetica Neue</family>
    <prefer><family>Liberation Sans</family></prefer>
  </alias>
  <alias>
    <family>Helvetica</family>
    <prefer><family>Liberation Sans</family></prefer>
  </alias>
  <alias>
    <family>sans-serif</family>
    <prefer><family>Liberation Sans</family></prefer>
  </alias>
</fontconfig>