According to Film Music Reporter, the composers are Alex Heffes and Anoushka Shankar. This is confirmed by Heffes's Wikipedia page (linked above) and Anoushka Shankar's Facebook page.
The website Soundtrack Mania lists the credited songs from season 1 and allows for listening.
Trailer: A Suitable Boy - Alex Heffes & Anoushka Shankar
Episode 1: Do Naina ...