Enys Men (2023)
Cornish folklore turns surreal. A lone volunteer tasked with making wildlife observations of a rare flower starts losing her grip onf realitiy. Remember that 15th Doctor episode 73 Yards? Yeah. Like that, but Cornish instead of Welsh. Bit of claustrophobia/agoraphobia. Body horror features amongst a carousel of disjointed images.
If this was aligned with a Magnus Archives fear entity, it'd be The Lonely.
Weird, understated, unnerving.