Star Wars Battlefront II (2005) was not released on GameCube. Platforms: PS2, Xbox, PC, PSP.
Pandemic/LucasArts prioritized PS2/Xbox/PC. GameCube's smaller install base and lack of online infrastructure (no built-in Ethernet, modem adapter rare) made the heavy multiplayer focus unviable.
For GC Battle Fix: Rogue Squadron III: Rebel Strike has split-screen co-op campaign and versus — closest experience.