Hey there ..
There is an issue with ultra wide monitors (3440x1440 or 2560x1080) .. the black bars dont go away even though the game does recognize the correct resolution ..
After todays big update, gameplay in 21:9 still has black bars
Another update today (118.6 MB) and the issue is still NOT fixed
Ya this is kind of a strange bug.
26 July 2018 Update .. 21:9 black bars issue (3440x1440) is still NOT fixed
03 August 2018 update did NOT fix the issue
10 August 2018 update, proper 21:9 support is still not available