There is no native support of ultrawide screen, but this way you can set any resolution. The game will run in borderless fullscreen windowed mode. Tested on Windows 11 in 3840x1080 resolution.

1. On game's page click to "Manage" (gear icon), then "Properties...".
2. On "General" tab under "Launch Option" add these parameters. Change pixel numbers to fit your screen.
-popupwindow -screen-width 3840 -screen-height 1080
3. Start the game and in the Configuration window tick on "Windowed". Do not change the "Screen resolution"!
4. Click on "Play!" and enjoy this awesome game on your ultrawide screen! :)