Crie o arquivo ~/.config/fontconfig/conf.d/10-prefer-hindi-gujr.conf
e forneça este conteúdo:
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<alias>
<family>serif</family>
<prefer>
<family>Lohit Devanagari</family>
<family>Lohit Gujarati</family>
</prefer>
</alias>
<alias>
<family>sans-serif</family>
<prefer>
<family>Lohit Devanagari</family>
<family>Lohit Gujarati</family>
</prefer>
</alias>
<alias>
<family>monospace</family>
<prefer>
<family>Lohit Devanagari</family>
<family>Lohit Gujarati</family>
</prefer>
</alias>
</fontconfig>