With OnePlus 6T launch, OnePlus contradicted itself by removing the headphone jack. Earlier they used to make fun of other companies for doing this but with 6T, they also boarded the same train. At least they provided an official Type-C to 3.5mm adapter with OnePlus 6T box.
When OnePlus 7 series went on sale, they stopped providing the Type-C to 3.5mm adapter also. OnePlus really wants their users to spend the money and get a pair of wireless earphones. Even the official adapter was out of stock since the OnePlus 7 series launch.
Luckily, they have silently restocked the official adapter and now you can buy it from their website by spending ₹390. Many users were complaining to OnePlus for the out of stock adapter from many weeks. It is finally here and you can now buy it for your OnePlus device.