The config that provides the most designer intended look for the Cantarell font-family on Linux

82-cantarell.conf

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fontconfig SYSTEM "../fonts.dtd">
<fontconfig>
  <!-- First, we apply the general rules -->
  <match target="font">
    <test name="family" compare="eq" ignore-blanks="true">
      <string>Cantarell</string>
    </test>
    <edit name="antialias" mode="assign">
      <bool>true</bool>
    </edit>
    <edit name="hinting" mode="assign">
      <bool>true</bool>
    </edit>
    <edit name="autohint" mode="assign">
      <bool>true</bool>
    </edit>
  </match>
  <!-- Then, we enable font hinting for Cantarell medium and bolder -->
  <match target="font">
   	<test name="family" compare="eq" ignore-blanks="true">
  	  <string>Cantarell</string>
  	</test>
    <test name="weight" compare="more">
      <const>regular</const>
    </test>
    <edit mode="assign" name="hintstyle">
      <const>hintslight</const>
    </edit>
  </match>
  <!-- Then, we disable font hinting for Cantarell regular and lighter -->
  <match target="font">
   	<test name="family" compare="eq" ignore-blanks="true">
  	  <string>Cantarell</string>
  	</test>
    <test name="weight" compare="less">
      <const>medium</const>
    </test>
    <edit mode="assign" name="hintstyle">
      <const>hintnone</const>
    </edit>
  </match>
</fontconfig>