62-firefox-symbola.conf

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>

<!-- If the Symbola font is installed, prevent it from being used, but don't blacklist
the actual font name as Firefox only supports this font family hardcoded for monochromatic
text presentation of emoji/symbols. VS15/default presentations. -->
<!-- deleting file property instead of family works too, and prevents chrome from segfaulting. -->

 <match target="scan">
    <test name="family">
        <string>Symbola</string>
    </test>
    <!-- <test name="prgname">
        <string>firefox</string>
    </test> -->
    <!-- <edit name="family" mode="delete" /> -->
    <edit name="file" mode="delete" />
</match>

<!-- This 2nd block makes the font family also represent the Symbola font.
It will still leave the font usable under it's original name, but
must prepend Symbola to the front of the list.. -->
<match target="scan">
    <test name="family" >
        <string>Noto Sans Symbols2</string>
    </test>
    <!-- <test name="prgname">
        <string>firefox</string>
    </test> -->
    <edit name="family" mode="prepend">
        <string>Symbola</string>
    </edit>
</match>

</fontconfig>