Games like The Outbreak Guardian
Games like The Outbreak Guardian include RimWorld, Kenshi, Infection Free Zone, Oxygen Not Included, and Big Ambitions. We matched them by the tags players give The Outbreak Guardian on Steam (Outbreak Sim, Time Management, Sandbox, Management, and Survival): closest matches first, and among equally close ones the better-known games.

RimWorld
Shared: Sandbox · Survival · Management

Kenshi
Shared: Sandbox · Survival · Open World

Infection Free Zone
Shared: Management · Strategy · Survival

Oxygen Not Included
Shared: Survival · Management · Sandbox

Big Ambitions
Shared: Management · Sandbox · Time Management

Factorio
Shared: Sandbox · Strategy · Survival

Dawn of Man
Shared: Survival · Strategy · Sandbox

Banished
Shared: Strategy · Survival · Sandbox

This War of Mine
Shared: Survival · Strategy · Choices Matter

Cities: Skylines
Shared: Management · Sandbox · Strategy

Manor Lords
Shared: Strategy · Management · Sandbox

Jurassic World Evolution
Shared: Management · Sandbox · Strategy

Global Rescue
Shared: Sandbox · Management · Strategy

Jurassic World Evolution 2
Shared: Management · Sandbox · Strategy

Totally Accurate Battle Simulator
Shared: Sandbox · Strategy · Simulation

Plague Inc: Evolved
Shared: Outbreak Sim · Strategy · Simulation

Kingdoms and Castles
Shared: Management · Sandbox · Strategy

Project Zomboid
Shared: Survival · Sandbox · Open World

Dwarf Fortress
Shared: Sandbox · Strategy · Management

Space Engineers
Shared: Sandbox · Survival · Simulation

Game Dev Tycoon
Shared: Management · Strategy · Simulation

Foundation
Shared: Sandbox · Management · Strategy

Amazing Cultivation Simulator
Shared: Sandbox · Strategy · Simulation

Planet Coaster
Shared: Sandbox · Management · Strategy