Shetland and Orkney have today a population together the size of Faroe, even through they have a far better climate and until the mid 19th century had a far larger population. So let's say that Denmark keep them and the timeline up to modern more or less stay minimal butterfly.
Denmark lose Norway in 1814, but keep these island together with Faroe, Iceland and Greenland.
The islands have of course been converted to Lutheranism together with Faroe in the 16th century.
Linguistic they're in same boat as the Faroese, the Danes doesn't create a separate bible for them, so their languages are seen as Danish dialects until the 19th century. So in short they all talk something we wouls recognise as Faroese.