Loved Murder on Middle Beach too. I check for updates on that heartbreaking case.
My recommendations.... Murders at White House Farm on HBOmax. Dramatized true story of a British case. Great acting, shocking story and one that sticks with you.
Equinox on Netflix. A fantastic new Danish series that delves into the disappearance of 22 high school students and the sister of one who investigates years later. Deals with occult rituals and is dark, but not gory. Loved it.
Oldenheim 12 and Shoendam (sp.?) 12 on Acorn (British subscription on Amazon) Dutch. Both addictive whodunnits.
The Missing. On Starz,but available on Amazon prime. Both seasons are great. Set in France, Germany, Belgium and UK, the first season starts slow,but is worth it. I immediately began binging season 2 after,and loved it more. There is a spin-off now called Baptiste( the weary compassionate detective from The Missing) on PBS Masterpiece. Just started,but good.
Department Q. Mysteries. Danish. Available on AMC+. If it isn't there anymore, rent them. These are my favorites. Dark and brooding with 2 detectives who investigate cold cases. The Absent One is the best. It is the second,but you don't need to watch them in order. I've rewatched them, and I wish there were more.
The Head on HBOmax. Whodunnit set in Antarctica, where a dark winter ends,and a researcher's headless body is found. Great to watch with coffee and covers.
I don't really care about series that are episodic...obv. there are exceptions, but these all revolve around a central mystery or case. I'd love feedback if you watch any of these. Hope you like them!