Not sure why this game is listed as 'native' ultrawide support? It does not. It requires you to edit config files manually to trick the game and even then you're presented with letterboxing where it shouldn't be on an ultrawide (since it's an ultrawide cutscene) and as of 2021 these tricks no longer seem to work for some people.
At the very least 'native' support should allow selection of a 21:9 resolution from the in-game settings, even if there are minor issues...