There's no changelog for this update, but I'm guessing it might have something to do with the change of banner on the start screen. More specifically, there's a banner linked to a fan survey that SI want feedback from to help them decide the future direction for the game.
Date Released: May 12th, 2021
File size: 262MB
21.4.0-1540115 List of Changes- Possibly a change of banner on start screen
If you encounter any issues post update, please use the official FAQ for troubleshooting suggestions. You can also contact [email protected] or use or SI's FM21 Bugs Forum for further support.