This Seeking Tech guide will explain how to disable cross-platform matchmaking in the PlayStation 5 version of XDefiant.
1. To start off, head to the Settings menu of the game.
2. From there, go to Matchmaking and Account.
3. Set the Crossplay setting to Off to disable it.
On the right side, you should see a note saying that the matchmaking may take longer, and there may result in more server latency, with this feature turned off.
As an alternate method, you can set Crossplay to On, and then set Input-Based Matchmaking to On. This will allow you to play with PC and Xbox players, while also limiting the matchmaking to players who are using controllers instead of keyboard and mouse.