Re: Apex Legends 21:9 Resolutions
You need to set windows desktop resolution on that monitor to your desired value prior to starting the game.
If you can get what-ever funky res running on the windows desktop the game will default to that as its "native" setting.
Now if your monitor doesnt support that res via windows you could try custom res in Nvidia control panel.
In playing around with this I find sometimes you get black borders instead of full screen, sometimes its fullscreen.
Good luck!