PC (Windows), Nintendo Switch (Legacy Edition), and Stadia (now defunct).
Because the game does not officially exist on this console, any direct "download" links claiming to be the official FIFA 21 for Xbox 360 are likely misleading or harmful. However, the dedicated FIFA community has found creative ways to keep the console alive through unofficial mods and legacy versions. The Reality of FIFA on Xbox 360 Xbox 360 Fifa 21 Download
If you want to play the actual FIFA 21 as intended by EA Sports, you will need one of the supported platforms: PC (Windows), Nintendo Switch (Legacy Edition), and Stadia