/etc/fonts/conf.d/ Current File: //etc/fonts/conf.d/56-language-selector-ar.conf
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
    <match target="pattern">
        <test name="lang">
            <string>ar</string>
        </test>
        <test qual="any" name="family">
            <string>sans-serif</string>
        </test>
        <edit name="family" mode="prepend">
            <string>Noto Sans</string>
            <string>Noto Sans Arabic UI</string>
        </edit>
    </match>
    <match target="pattern">
        <test name="lang">
            <string>ar</string>
        </test>
        <test qual="any" name="family">
            <string>serif</string>
        </test>
        <edit name="family" mode="prepend">
            <string>Noto Serif</string>
            <string>Noto Naskh Arabic</string>
        </edit>
    </match>
</fontconfig>