 I thought I should reply to my own original post. As it turned out when I got to my client site to do further work, the cable that was being used was an HDMI to DisplayPort. I replaced it with a couple of spare HDMI cables and was then able to get 2560x1080 Ultrawide resolution. So the onboard Intel UHD 630 graphics does output in an ultrawide resolution. The 1920x1080 resolution limitation I was experiencing seem to be cable related. The odd thing is that the same cable and monitor was connected to an older Dell Optiplex 9010 and it did work at the proper resolution.
I just purchased three refurb Dell OptiPlex 3070 machines for a client. It turns out two of their monitors are LG Ultrawide monitors. The systems are running Windows 11 Pro and are connected as DisplayPort monitors using the on board Intel Integrated UHD Graphics 630. I can't get a resolution beyond 1920x1080 so I am looking for assistance on whether the UHD 630 would support a Ultrawide screen resolution. If not, what entry-level GPU would be recommended for the 3070. These are essentially "office" machines so most of the work is web or text apps so nothing fancy or fast is needed.  
Optiplex 3070 Graphics for Ultrawide Monitor