The UI is broken on ultra-wide screen (3440x1440) for the panel where you choose terrain in main menu. Top bit of it is not visible as it is off screen. The "Welcome to Terra Nil" has the "0% of 50%" circle over the text, again probably cause of the alignment. Popup/tooltip for the bottom-left circle, again off-screen.
You need to test the game against ultra-wide. In Unity you can add new resolutions to test in the aspect ratio drop-down in game view.
More and more people have access to these kinds of resolutions so you need to either add support for it or you need to lock the game res to aspect ratios you designed for so that we have black borders on sides when game will not work well on ultra-wide.
Sorry we overlooked this! Until an update's released that has better resolution-independent support, you can run the game using command line parameters to force a 16:9 (windowed?) aspect ratio.
(Whenever I do this for something I might use often, I make a shortcut to the executable and the command line parameters to the shortcut's properties.)
e.g. TerraNil.exe -screen-height 1920 -screen-width 1080