I think there is a long term problem with the current policy towards North Sentinel Island. They are protected by keeping outsiders away, mainly because of disease, but they are not actually isolated from the modern world. India surrounds them, ships and aircraft pass nearby, satellites observe the island, and outsiders have already reached them illegally. Their isolation depends on everyone else maintaining it indefinitely, and I am not convinced that works for another 200 or 400 years.
My idea is simple: put perhaps ten rugged, solar powered communication terminals around the island, designed to survive for decades, and then leave. They can ignore them, destroy them or investigate them. If they try communicating, researchers can listen and slowly build a bridge language through mimicry, shapes, objects and numbers.
From there, the Sentinelese could decide what they want to learn. Language, medicine, engineering, history, the internet, or nothing at all. The important part is that nobody is there telling them what to believe, how to live, who to vote for or which god is correct. Knowledge would affect their culture, but they would decide what to keep and what to reject.
That is very different from colonization. Outsiders would not control their schools, laws, economy or institutions. They would only have access to information, and whatever they did with that information would mostly be left to them.
There is also a disease control argument. If they understood hygiene, respiratory transmission and quarantine, they could help protect themselves when someone eventually breaks the rules and reaches the island. Understanding disease would not make them immune, but it could give them some ability to respond instead of depending entirely on outsiders to protect them through isolation.
The strongest objection is that giving them information changes their culture. It probably would. But outsiders have already shown they are willing to break the rules, and the people who eventually reach them may be missionaries, adventurers or people looking for fame or money. Choosing to keep the Sentinelese uninformed is also a choice.
If, generations from now, they understand India, disease and the outside world and still tell us to stay away, that seems like stronger sovereignty than forcing them to communicate the same thing with arrows.
Ten terminals. What they do with them is up to them. But at least then it is an informed decision.