I like the "fairly grim European mystery" genre of TV quite a lot in general, and Shetland is one of my recent favorites. It's based on a series of books by Ann (not of) Cleeves (I haven't read them yet but I want to!) about detective inspector Jimmy Perez, a police detective in the Shetland islands. The show has a nice mix of cases with character development and is slightly lighter than, say, Hinterland. (Which I also love!) The portrayal of the very specific Shetland culture is fascinating, and Perez's prickly but loving co-parenting relationship with the biological father of his late wife's daughter is a particular highlight.
In the U.S., the first three seasons of Shetland are on Netflix, and the fourth is currently being released on BritBox.