Games like Mechajammer
Games like Mechajammer include Cyberpunk 2077, XCOM 2, Fallout 4, Warhammer 40,000: Mechanicus, and Shadowrun Returns. We matched them by the tags players give Mechajammer on Steam (Sci-fi, Tactical, Singleplayer, Atmospheric, and Open World): closest matches first, and among equally close ones the better-known games.

Cyberpunk 2077
Shared: Open World · Singleplayer · Cyberpunk

XCOM 2
Shared: Tactical · Turn-Based Combat · Sci-fi

Fallout 4
Shared: Singleplayer · Open World · Atmospheric

Warhammer 40,000: Mechanicus
Shared: Sci-fi · Turn-Based Combat · Singleplayer

Shadowrun Returns
Shared: Sci-fi · Cyberpunk · Singleplayer

STAR WARS Zero Company™
Shared: Sci-fi · Singleplayer · Tactical

Deus Ex: Mankind Divided
Shared: Sci-fi · Cyberpunk · Atmospheric

Starfield
Shared: Singleplayer · Sci-fi · Open World

Fallout: A Post Nuclear Role Playing Game
Shared: Open World · Sci-fi · Singleplayer

XCOM: Enemy Unknown
Shared: Tactical · Sci-fi · Singleplayer

Fallout: New Vegas
Shared: Open World · Singleplayer · RPG

Stray
Shared: Singleplayer · Atmospheric · Cyberpunk

Cloudpunk
Shared: Sci-fi · Atmospheric · Open World

Wasteland 2: Director's Cut
Shared: Tactical · RPG · Singleplayer

XCOM®: Chimera Squad
Shared: Singleplayer · Sci-fi · Tactical

Fallout 2: A Post Nuclear Role Playing Game
Shared: Open World · Singleplayer · Turn-Based Combat

UnderRail
Shared: Sci-fi · Singleplayer · Turn-Based Combat

Shadowrun: Dragonfall - Director's Cut
Shared: Sci-fi · Cyberpunk · Singleplayer

The Last Spell
Shared: Singleplayer · Tactical · Turn-Based Combat

S.T.A.L.K.E.R. 2: Heart of Chornobyl - Standard Edition
Shared: Open World · Atmospheric · Singleplayer

No Man's Sky
Shared: Sci-fi · Open World · Exploration

Encased: A Sci-Fi Post-Apocalyptic RPG
Shared: Turn-Based Combat · Sci-fi · CRPG

Quasimorph
Shared: Singleplayer · Turn-Based Combat · RPG

MENACE
Shared: Tactical · RPG · Turn-Based Combat