Where in India can macadamia actually grow and is it worth trying?

Macadamia is climate restricted in India and is not a crop you can plant anywhere. It needs a mild subtropical to cool tropical climate without extreme heat, and does best in select hill and high elevation pockets, for example parts of the Nilgiris, Coorg, the Western Ghats hills and some northeastern and Himalayan foothill areas with suitable temperature and rainfall. In the hot plains it generally does not perform. It is also a long gestation tree, taking many years to come into proper bearing. There is very limited commercial cultivation and limited organised buyer network in India compared to coffee or cashew, so market access is a real concern. Before planting, confirm suitability for your exact location with a horticulture university or KVK, and line up where you will sell the nuts, because a high value crop with no buyer is a loss.