have you tried a different connection method like displayport etc
in CRU or even the nvidia control panel etc if nvidia , create a 21:9 resolution higher then the 4k one if that is the issue you think , just dont use the higher resolution
see https://www.reddit.com/r/swtor/comments/e2k9cc/possible_fix_for_aspect_ratio_bugs_219_169_1610/
@proxos666 I have tried everything :
Hdmi cables - from cheap to expensive
Display port cables - from cheap to expensive
Tried CRU to delete resolutions on EDID Override...
Tried making a higher resolution on 21:9...
Nothing worked...
That dreadful 4k resolution is still there...and the higher resolution is not shown in windows - but in Nvidia control panel i can choose it...
did you try the below from the reddit link ?
Not sure if you already got it fixed by now, but in order to get 5120x2160 you have to disable DRS, go to the resolution settings in Nvidia control panel, highlight your native resolution then click customize. Now you can create 5120x2160
