/etc/fonts/local.conf

local.conf

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
  <match target="pattern">
    <test qual="any" name="family"><string>Helvetica</string></test>
    <edit name="family" mode="assign" binding="same"><string>Liberation Sans</string></edit>
  </match>
  <alias>
    <family>serif</family>
    <prefer>
      <family>EmojiOne Color</family>
      <family>Liberation Serif</family>
      <family>FreeSerif</family>
      <family>DejaVu Serif</family>
    </prefer>
  </alias>
  <alias>
    <family>sans-serif</family>
    <prefer>
      <family>EmojiOne Color</family>
      <family>Liberation Sans</family>
      <family>FreeSans</family>
      <family>DejaVu Sans</family>
    </prefer>
  </alias>
  <alias>
    <family>monospace</family>
    <prefer>
      <family>EmojiOne Color</family>
      <family>Meslo LG S</family>
      <family>Ubuntu Mono</family>
      <family>Liberation Mono</family>
      <family>DejaVu Sans Mono</family>
      <family>FreeMono</family>
    </prefer>
  </alias>
</fontconfig>