Same here. “Google Indic Keyboard” for mobile is famous among common people to write in Tamil language. But in desktop we don’t have an easy solution except “Google Input Tools”. In some professional use cases people are using Windows Tamil fonts/keyboard.
Anyway it is no longer supported to add “Google Input Tools” on websites using JavaScript. Instead either it should be used by the Chrome extension or in the URL https://www.google.com/inputtools/try/. So we can close this topic.