Is there a tag somewhere on it? There certainly should be a Service Tag (as do all Dells) and you can look up the specs... this aside, I looked up the specs for XPS 8920 desktop. Unfortunately it's a "low-end consumer computer". I has "onboard video" which in my mind has always been a no-no for multi-monitor setups (though some people get them to work). Your XPS has at least 1, PCIE x16 slot on the mobo. That's what you need for a proper video card. I'm presuming you want to run 3 or 4 monitors ?? I suggest you skip the onboard video connection and buy a proper 4-port video card... like Quadro T600. Set that up in your present computer. If you can't get it to run correctly, you won't be "out anything", as you'll want to get an upgraded computer and you could use the T600 in it.
Dell used to have a "21 day free return, no questions asked" policy. Are you within the 21 days? I could direct you to a really great computer for $1100... or one almost as good for $300-$400 if you were interested.
When I ordered it, I was VERY specific it had to have video cards for multiple monitors. But I don't think this has "dedicated video cards". Sounds like what I have is a large video card that can become 4 virtual video cards.
You should have a dedicated video card plugged into the x16 slot. You MAY have your monitors plugged into the "onboard video" chip ports... which may be the problem. And yes W11 may possibly not be "ready for prime time" when it comes to multi-monitor displays.
I would not trust them. They mostly/only(?) have low-end, consumer grade (junk). Ideally what you really need is a proper workstation machine and a proper video card.
Have you tried bringing up the video card settings on a working monitor and simply disable two monitors and make that the only primary?
Ordered it early September. First box didn't work at all. I think the guy said the "motherboard was defective". I returned that one. they sent me another- 4 months ago. So this one worked 3 months, now crapping out. One thing for sure, DELL is not going to badmouth Windows 11. Take that to the bank. I need to find a solution to this ASAP. Yes, where can I get a box that will work?