High Quality Lesser Watched TV series
Babylon Berlin: https://www.youtube.com/watch?v=HAn3RXeCrLg&t=26s
A political/crime noir set in 1920s Weimar Germany a few years to the rise of the Nazis - one of the most fascinating historical periods of the 20th century.
Warrior: https://www.youtube.com/watch?v=79rtcCnaeyo
A Bruce Lee inspired martial arts/gangster period drama set in 1870s San Francisco dealing with the issues of Chinese immigration to the city. Pretty fictionalised.
Balkan Shadows: https://www.youtube.com/watch?v=zjvemFdrbRk&t=34s
A bit rough around the edges, but a noir period drama set in 1930s Yugoslavia (or now modern Serbia). Similar to Babylon Berlin.
Counterpart: https://www.youtube.com/watch?v=JRuaNHLp6OU
A sci-fi espionage series set in an alternative present where the earth split into two worlds in two different universes in the 1980s, separated by a tunnel. Every single person alive in the 1980s was effectively cloned, or born in two separate worlds as they diverged.
I'd add a few Korean ones too, but man the trailers for them are bad: Arthdal Chronicles and Happiness.