New York Times / NYT Magazine are the ones the stand out, but US centric (understandably). Here's a recent photo essay and article I liked:
Most Americans think they know the story of the pandemic. But when a writer immersed himself in a Covid oral-history project, he realized how much we’re still missing.
www.nytimes.com
They had some good long form essays on the 20-year anniversary of the Iraq war as well:
I learned that there is no such thing as an objective narrator in human conflict.
www.nytimes.com
NYT is behind a paywall but it's worth it imo.
In the UK, FT Weekend are my go to for photo stories, they're always commissioning interesting photographers.
An unlikely source would be newsletters - many photographers I admire and follow use Substack and they post long form journals every now and then