I personally do not see people posting content in Devanagari script on websites very often. I do see the use of Hinglish which is written in English script.
I get a lot of messages on WhatsApp written in Devanagari script but they are mostly forwards… I don’t see people often making an effort to write in Devanagari themselves.
There are very few people who actually know how to write in Devanagari using OS fonts, myself included. For that using Google Indic Keyboard or Google Input Tools is the way to go.