To turn off crossplay for the Xbox Series X and Xbox Series S versions of XDefiant, you can check out this guide at Seeking Tech.
1. You won’t be able to disable crossplay inside the game. Instead, head over to the Settings menu of your Xbox console.
2. You then need to go to Account.
3. Go to Privacy & online safety.
4. Select Xbox privacy
5. Head over to View details & customize.
6. Go to Communication & multiplayer.
7. Set the “You can join cross-network play setting” to Block.
This will disable crossplay for all games on your Series X or Series S consoles, including XDefiant.