Games like Operator: Observation
Games like Operator: Observation include Outer Wilds, Escape the Backrooms, Five Nights at Freddy's: Security Breach, DREDGE, and Firewatch. We matched them by the tags players give Operator: Observation on Steam (Adventure, Interactive Fiction, Outbreak Sim, Exploration, and Time Management): closest matches first, and among equally close ones the better-known games.

Outer Wilds
Shared: Exploration · Adventure · Mystery

Escape the Backrooms
Shared: Horror · Adventure · Exploration

Five Nights at Freddy's: Security Breach
Shared: Horror · Exploration · Adventure

DREDGE
Shared: Exploration · Adventure · Mystery

Firewatch
Shared: Adventure · Exploration · Mystery

PEAK
Shared: Adventure · Exploration · 3D

CARIMARA: Beneath the forlorn limbs
Shared: Adventure · Exploration · Mystery

Amnesia: A Machine For Pigs
Shared: Horror · Exploration · Interactive Fiction

Sally Face - Episode One
Shared: Adventure · Horror · Psychological Horror

Inside the Backrooms
Shared: Horror · Adventure · Exploration

Lethal Company
Shared: Horror · Exploration · Psychological Horror

Who's Lila?
Shared: Interactive Fiction · Horror · Psychological Horror

What Remains of Edith Finch
Shared: Adventure · Exploration · Mystery

Stray
Shared: Adventure · Exploration · Singleplayer

Poppy Playtime
Shared: Horror · Adventure · Mystery

Bad Parenting 1: Mr. Red Face
Shared: Adventure · Horror · 3D

Psalm 5:9-13
Shared: Exploration · Horror · Psychological Horror

Subnautica 2
Shared: Exploration · Horror · Adventure

Scanner Sombre
Shared: Exploration · Adventure · Horror

Caravan SandWitch
Shared: Adventure · Exploration · Interactive Fiction

Amanda the Adventurer 3
Shared: Adventure · Interactive Fiction · Exploration

Amanda the Adventurer 2
Shared: Adventure · Interactive Fiction · Exploration

Mirror 2: Project X
Shared: 3D · Interactive Fiction · Adventure

Until Dawn™
Shared: Adventure · Interactive Fiction · Horror