Games like Flotsam
Games like Flotsam include Timberborn, Factorio, RimWorld, Oxygen Not Included, and Dwarf Fortress. We matched them by the tags players give Flotsam on Steam (Base Building, Colony Sim, City Builder, Sandbox, and Resource Management): closest matches first, and among equally close ones the better-known games.
Timberborn
Shared: Colony Sim · City Builder · Sandbox
Factorio
Shared: Base Building · Automation · Sandbox
RimWorld
Shared: Base Building · Colony Sim · Sandbox
Oxygen Not Included
Shared: Base Building · Colony Sim · Resource Management
Dwarf Fortress
Shared: Colony Sim · Base Building · City Builder
Frostpunk
Shared: City Builder · Resource Management · Colony Sim
Satisfactory
Shared: Base Building · Automation · Open World
Kingdoms and Castles
Shared: Colony Sim · City Builder · Resource Management
Manor Lords
Shared: City Builder · Base Building · Sandbox
Banished
Shared: Colony Sim · City Builder · Survival
Dyson Sphere Program
Shared: Base Building · Automation · Resource Management
Against the Storm
Shared: Base Building · City Builder · Colony Sim
Space Haven
Shared: Base Building · Colony Sim · Survival
Prison Architect
Shared: Base Building · Sandbox · Colony Sim
Endzone - A World Apart
Shared: City Builder · Base Building · Survival
Empires of the Undergrowth
Shared: Base Building · City Builder · Colony Sim
The Crust
Shared: Base Building · Colony Sim · Automation
The Wandering Village
Shared: City Builder · Colony Sim · Resource Management
Settlement Survival
Shared: City Builder · Colony Sim · Sandbox
They Are Billions
Shared: Base Building · Colony Sim · City Builder
Workers & Resources: Soviet Republic
Shared: City Builder · Base Building · Colony Sim
Dawn of Man
Shared: Colony Sim · City Builder · Survival
Going Medieval
Shared: Base Building · Colony Sim · City Builder
Planetbase
Shared: Colony Sim · Base Building · City Builder