Games like Groundless
Games like Groundless include Stick Fight: The Game, Overcooked! 2, Duck Game, Move or Die, and SpeedRunners. We matched them by the tags players give Groundless on Steam (Action, Indie, Local Multiplayer, 4 Player Local, and Local Co-Op): closest matches first, and among equally close ones the better-known games.

Stick Fight: The Game
Shared: Action · Local Multiplayer · Multiplayer

Overcooked! 2
Shared: Local Co-Op · Multiplayer · 4 Player Local

Duck Game
Shared: Local Multiplayer · Action · Multiplayer

Move or Die
Shared: Action · Local Multiplayer · Multiplayer

SpeedRunners
Shared: Local Multiplayer · Indie · Multiplayer

Gang Beasts
Shared: Action · Multiplayer · Local Multiplayer

Overcooked
Shared: Indie · Local Co-Op · Multiplayer

Broforce
Shared: Action · Local Co-Op · Indie

TowerFall Ascension
Shared: Indie · Local Multiplayer · Action

Lovers in a Dangerous Spacetime
Shared: 4 Player Local · Local Co-Op · Local Multiplayer

Pummel Party
Shared: 4 Player Local · Multiplayer · Local Multiplayer

Bopl Battle
Shared: Action · 4 Player Local · Multiplayer

Crawl
Shared: Local Multiplayer · 4 Player Local · Indie

Brawlhalla
Shared: Multiplayer · Local Multiplayer · Action

Rivals of Aether II
Shared: Indie · Action · Local Multiplayer

Streets of Rage 4
Shared: Action · Indie · Local Multiplayer

Ultimate Chicken Horse
Shared: Multiplayer · Local Co-Op · Local Multiplayer

Kopanito All-Stars Soccer
Shared: Action · Local Multiplayer · Indie

Unrailed!
Shared: Multiplayer · Local Co-Op · Action

Rivals of Aether
Shared: Indie · Local Multiplayer · Multiplayer

Moving Out
Shared: Action · Indie · Local Multiplayer

ROUNDS
Shared: Local Multiplayer · Multiplayer · Action

FORCED: Slightly Better Edition
Shared: Action · Indie · Local Co-Op

Awesomenauts
Shared: Action · Indie · Multiplayer