You can't directly change your Steam Deck username. The username displayed on your Steam Deck is tied to your Steam account. To change your username, you'll need to modify your Steam account settings.
Here's how to change your Steam account username:
- Log in to your Steam account on your computer or through the Steam website.
- Click on your username in the top-right corner of the screen.
- Select "Account Details" from the dropdown menu.
- Click on "Edit Profile".
- Enter your desired username in the "Profile Name" field.
- Click "Save Changes".
Once you've saved the changes, your new username will be reflected on your Steam Deck and across all other Steam platforms.