conf.d/11-lcdfilter-legacy.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<!--  Use lcdlegacy as default for LCD filter -->
  <match target="font">
    <edit mode="assign" name="lcdfilter">
      <const>lcdlegacy</const>
    </edit>
  </match>
</fontconfig>