If you're playing Yu-Gi-Oh Master Duel on Steam, you've likely ran into the issue of the game opening in Windowed mode, when you'd rather play in Fullscreen. Even if you set the game to Fullscreen from the game's settings, the next time you open it, it'll go back to Windowed. Well, we have a solution! ...Sorta.
You can set the game to open in Windowed Fullscreen. It's not true Fullscreen, as the game and other programs will still register as being in Windowed mode, but it'll completely get rid of borders, and it'll fill out the entire screen. Also, this might not work for everyone, especially Linux users.
How To Force the Game To Open in Fullscreen
The process is quite simple. In your Library, right-click on Yu-Gi-Oh Master Duel -> Properties -> Launch Options -> type the following line:
And that's about it! The next time you launch the game, and every time after that, it'll enter Windowed Fullscreen.