Not actually the bare minimum base game by Sumi
Very little content base game so you can build off it. Totally permissive, you can relicense it or do whatever.
Templates
A collection by dibesfer
Very basic foundations of a game
Packages
Cave Game by olive
The simplest block game.
Void - An empty game by Linuxdirk
The purpose of this game is to test mods in an absolutely “clean” environment with absolutely no “3rd-party” mods