Games like Nyctophobia
Games like Nyctophobia include Firewatch, What Remains of Edith Finch, SOMA, Lethal Company, and Layers of Fear (2016). We matched them by the tags players give Nyctophobia on Steam (Adventure, Walking Simulator, Exploration, Horror, and Atmospheric): closest matches first, and among equally close ones the better-known games.

Firewatch
Shared: Adventure · Walking Simulator · Atmospheric

What Remains of Edith Finch
Shared: Walking Simulator · Atmospheric · Adventure

SOMA
Shared: Horror · Atmospheric · Exploration

Lethal Company
Shared: Horror · First-Person · Exploration

Layers of Fear (2016)
Shared: Horror · Walking Simulator · Atmospheric

Scanner Sombre
Shared: Walking Simulator · Exploration · Adventure

ROUTINE
Shared: Adventure · Atmospheric · Sci-fi

Amnesia: A Machine For Pigs
Shared: Walking Simulator · Horror · Atmospheric

Still Wakes the Deep
Shared: Horror · Walking Simulator · First-Person

Stray
Shared: Adventure · Atmospheric · Exploration

Outer Wilds
Shared: Exploration · Adventure · Atmospheric

Outlast
Shared: Horror · First-Person · Atmospheric

Valley
Shared: Adventure · Exploration · First-Person

Subnautica
Shared: Horror · Exploration · Adventure

Among the Sleep - Enhanced Edition
Shared: Adventure · Horror · Atmospheric

Iron Lung
Shared: Horror · Atmospheric · Adventure

NaissanceE
Shared: Exploration · Walking Simulator · Atmospheric

Journey
Shared: Adventure · Atmospheric · Exploration

Five Nights at Freddy's: Secret of the Mimic
Shared: Adventure · Horror · First-Person

The Long Dark
Shared: Exploration · Adventure · Atmospheric

Cairn
Shared: Exploration · Adventure · Stylized

Amenti
Shared: Adventure · Horror · Exploration

KARMA: The Dark World
Shared: Walking Simulator · Horror · Atmospheric

Subnautica 2
Shared: Horror · Exploration · Adventure