Make sure you are using a display port cable also.
I use an Acer Predator X34p ultrawide, have no issues at all with the aspect ratio.
The menus will always look 16:9.
The game does not currently support Ultrawide monitors, at least in replays and flashbacks. There is already a thread about this.
For me it is completely incomprehensible why Ultrawide monitors are no longer completely supported by EA-Codemasters. This has always worked exemplary in the past years. The problem exists only now in F1-2023. See also the attached screenshot:
Yeah, I had seen that post but because they were able to have it fit for racing etc., I imagine it's a different issue
