No Stem Darkening - Font.conf?

[Erick Rodriguez]

Good afternoon,

I've used stem darkening with FreeType on Linux many times before, by enabling 
an environment variable like so:

FREETYPE_PROPERTIES="cff:no-stem-darkening=0 autofitter:no-stem-darkening=0"

I was wondering if there is a way to enable this through etc/fonts/conf.d? 
Basically, I want to enable stem darkening on one specific font only. This is a 
.conf file I've succesfully created:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<match target="font">
    <test name="family" qual="any">
      <string>Inter</string>
    </test>
    <edit name="hintstyle" mode="assign">
      <const>hintnone</const>
    </edit>
  </match>
</fontconfig>

Now I want to somehow get stem darkening in there, so that it only gets enabled 
for the font "Inter". Is this possible?

Your help is greatly appreciated!