Disclosure: Microsoft and Dell are clients of the author.
Windows 11 is in early preview right now, and it is far from feature complete; this phase of the deployment is typically focused on assuring hardware and application compatibility. Most of my newest desktop machines won’t yet run Windows 11 because they weren’t configured with their 2.0 Trusted Platform Modules (TPMs) turned on (an easy fix) or with Secure Boot enabled (a much more complicated fix).
I was, however, able to load the Windows 11 preview onto my Dell OptiPlex 7070 Ultra modular desktop successfully and without issues. If you decide to try out Windows 11, I suggest you load it overnight, as the upgrade takes several hours.