I don’t know if you are aware of them or not, but a similar situation is faced by the Kalash in Pakistan. They are remnants of Indo-Europeans (and Indo-Iranian religion) surrounded by a large population of Muslims. Related people in Afghanistan and Pakistan were forced to convert or die from a period of 80-100 years ago, and other populations of these people were displaced and wiped out in wars by the Muslim Emir Abdur Rahman Khan in the 1890’s. So the Kalash today are a remnant of a remnant.