Games like Undercraft
Games like Undercraft include Terraria, Rust, Valheim, Raft, and Don't Starve Together. We matched them by the tags players give Undercraft on Steam (Open World Survival Craft, Sandbox, Survival, Procedural Generation, and Multiplayer): closest matches first, and among equally close ones the better-known games.

Terraria
Shared: Open World Survival Craft · Sandbox · Survival

Rust
Shared: Survival · Open World Survival Craft · Multiplayer

Valheim
Shared: Open World Survival Craft · Survival · Online Co-Op

Raft
Shared: Open World Survival Craft · Survival · Multiplayer

Don't Starve Together
Shared: Open World Survival Craft · Survival · Multiplayer

ARK: Survival Evolved
Shared: Open World Survival Craft · Survival · Multiplayer

Palworld
Shared: Survival · Open World Survival Craft · Multiplayer

7 Days to Die
Shared: Survival · Open World Survival Craft · Multiplayer

Green Hell
Shared: Open World Survival Craft · Survival · Multiplayer

Starbound
Shared: Open World Survival Craft · Sandbox · Survival

Once Human
Shared: Survival · Multiplayer · Open World Survival Craft

Project Zomboid
Shared: Survival · Open World Survival Craft · Sandbox

Conan Exiles Enhanced
Shared: Survival · Open World Survival Craft · Sandbox

Grounded
Shared: Survival · Open World Survival Craft · Multiplayer

No Man's Sky
Shared: Open World Survival Craft · Survival · Multiplayer

The Forest
Shared: Open World Survival Craft · Survival · Adventure

Craftopia
Shared: Survival · Open World Survival Craft · Sandbox

Core Keeper
Shared: Survival · Sandbox · Multiplayer

Necesse
Shared: Open World Survival Craft · Sandbox · Multiplayer

RuneScape: Dragonwilds
Shared: Survival · Open World Survival Craft · Multiplayer

Enshrouded
Shared: Survival · Multiplayer · Online Co-Op

ICARUS
Shared: Open World Survival Craft · Survival · Multiplayer

Don't Starve
Shared: Open World Survival Craft · Survival · Sandbox

ARK: Survival Ascended
Shared: Survival · Multiplayer · Sandbox