https://joshuaproject.net/countries/IN
The Joshua Project website has information on Unreached People Groups that Speak Tamil. This website link is about India and the unreached people groups in India.
Please also go to the home page and put the word Tamil in the search engine.
It should take you here.
https://joshuaproject.net/languages/tam
You may put the name of a language, people group, country or resource in
the search engine.
https://joshuaproject.net/